Showing papers by "University of the Witwatersrand published in 1987"

Geomorphic evolution of Southern Africa since the Mesozoic

Abstract: Controversies regarding the correlation of erosion cycles within southern Africa are traced through some earlier contributions; many of these reflect a failure to apply rigorous field criteria to problems of mapping. The analysis of sections linking key coastal deposits to planation remnants in the interior is used to extrapolate field observations over wider areas. The resulting map of erosion surfaces, and contour plans of elevations on the more important of these, form the basis of the paper. A consistent datum is provided by the oldest of the surfaces (the African) through the diagnostic deep weathering profiles and duricrust cappings associated with it. The Great Escarpment was formed following continental rifting, and its survival up to the present as a major topographic feature is, in large measure, a function of the high elevations consequent upon the central position of southern Africa in Gondwanaland prior to this event. There is conclusive evidence for the co-existence of surfaces of the same age at different elevations inland of and below the Great Escarpment. This vertical separation can be ascribed to the existence, from early times, of separate base-levels for the plateau and coastal areas. The onshore evidence of erosion surfaces is correlated with recent data on offshore sedimentation, and reveals that a single cycle of erosion (interrupted by minor tectonic interludes) prevailed from the time of rifting to the early Miocene. By the end of this period a gentle pediplain (the African surface) extended across most of southern Africa at elevations of 500-600 m. Most erosion and scarp recession occurred during the earlier part of this interval and produced thick late Jurassic and Cretaceous sedimentary sequences, but shelf sedimentation declined during the Tertiary and had virtually ceased by the Oligocene, when interior planation had advanced to a stage where sediment supply to most rivers was minimal. Modest renewed uplift of 150-300 m in the Miocene tilted the continent slightly to the west and initiated a new (Post-African J) landscape cycle. This was accompanied by renewed offshore sedimentation, although at lower rates than during the Cretaceous. The cycle was terminated near the end of the Pliocene, and its relatively short duration resulted in imperfect planation in most areas to levels of no more than 100-300 m below the African surface. A second uplift of major proportions at the end of the Pliocene raised the eastern interior of the sub-continent by as much as 900 m, although much smaller movements characterized the western areas and interior axes of uplift. Major monoclinal warping resulted in the southeastern hinterland. The ensuing Post-African II cycle is manifested chiefly in deep incision of the coastal hinterland and downcutting along major rivers of the interior. Earlier surfaces were severely deformed and dissected, especially in the south-east of the country. Planation was limited to a few areas close to the coast. The resulting sedimentation is evident mainly in the offshore deltas of major rivers owing to the late development of vigorous coastal currents, but a major increase is reflected throughout the deeper ocean basins. The successive uplifts to which the continent was subject produced major changes in drainage patterns, although the evidence for pre-Miocene distributions is tenuous in many areas. The preservation of discrete erosion surfaces with separating escarpments over considerable periods not only confirms the episodic nature of these uplifts, but indicates a dominance of backwearing over down wearing in the geomorphic evolution of the sub-continent. The mechanisms controlling the uplift of southern Africa and similar passive continental margins are of considerable importance in the light of an increasing awareness that many elevated areas within the continents can be ascribed to such movements. Some thoughts are offered towards the formulation of a tectonic model which takes account of the evolutionary scheme now established for southern Africa.

The Schur multiplier

Abstract: During the last thirty years, a large amount of research has been devoted to the study of various properties of the second cohomology group H 2 (G,C*), also known as the Schur multiplier of a group G. The present book ties together various threads of the development, and conveys a comprehensive picture of the current state of the subject. In clear, carefully developed format, this work offers a unified treatment of a wealth of important results, and provides a wide range of mathematical techniques applicable to this subject. The book is written on the assumption that the reader has had the equivalent of a standard first-year graduate algebra course. Apart from a few specific results and the general knowledge presupposed, the book is entirely self-contained. This book is intended for research mathematicians.

An equation for the conductivity of binary mixtures with anisotropic grain structures

Abstract: An equation is presented which describes the conductivity (resistivity) of a wide variety of binary macroscopic mixtures as a function of the conductivities (resistivities) of the components, the volume (area) fraction of each, and two parameters. Unlike in an earlier version, the granular shape of at least one component is no longer required to be roughly spherical (circular). One parameter is the critical volume (area) fraction. The other, the exponent, is a combination of effective demagnetisation coefficients and the critical fraction. The equation, which is valid for all volume fractions, is shown to fit a variety of experimental data very well. Some deductions about the shape of the grains in the media can be made by analysing the experimental results.

Corporate Objectives in Sports Sponsorship

Abstract: This article considers corporate objectives in sports sponsorship. The important question is to determine why companies sponsor sport when there are other promotion techniques available to them. Reasons for sponsoring sport in the first place are discussed, as well as broad corporate objectives in becoming involved in sponsorships. This study involved a sample of 45 sponsors who received media exposure in South Africa between November 1984 and March 1985. Results show that the most important reasons for sponsoring sport include potential TV coverage, promoting the corporate image and the potential of spectators as customers. Anonymous sponsorship, even philanthropic, is rare.

The effects of fruit juices and fruits on the absorption of iron from a rice meal.

Abstract: The effects of the chemical composition of fruit juices and fruit on the absorption of iron from a rice (Oryza sativa) meal were measured in 234 parous Indian women, using the erythrocyte utilization of radioactive Fe method. The corrected geometric mean Fe absorptions with different juices varied between 0.040 and 0.129, with the variation correlating closely with the ascorbic acid contents of the juices (rs 0.838, P less than 0.01). Ascorbic acid was not the only organic acid responsible for the promoting effects of citrus fruit juices on Fe absorption. Fe absorption from laboratory 'orange juice' (100 ml water, 33 mg ascorbic acid and 750 mg citric acid) was significantly better than that from 100 ml water and 33 mg ascorbic acid alone (0.097 and 0.059 respectively), while Fe absorption from 100 ml orange juice (28 mg ascorbic acid) was better than that from 100 ml water containing the same amount of ascorbic acid (0.139 and 0.098 respectively). Finally, Fe absorption from laboratory 'lemon juice' (100 ml orange juice and 4 g citric acid) was significantly better than that from 100 ml orange juice (0.226 and 0.166 respectively). The corrected geometric mean Fe absorption from the rice meal was 0.025. Several fruits had little or no effect on Fe absorption from the meal (0.013-0.024). These included grape (Vitis vinifera), peach (Prunus persica), apple (Malus sylvestris) and avocado pear (Persea americana). Fruit with a mild to moderate enhancing effect on Fe absorption (0.031-0.088) included strawberry (Fragaria sp.) (uncorrected values), plum (Prunus domestica), rhubarb (Rheum rhaponticum), banana (Musa cavendishii), mango (Mangifera indica), pear (Pyrus communis), cantaloup (Cucumis melo) and pineapple (Ananas comosus) (uncorrected values). Guava (Psidium guajava) and pawpaw (Carica papaya) markedly increased Fe absorption (0.126-0.293). There was a close correlation between Fe absorption and the ascorbic acid content of the fruits tested (rs 0.738, P less than 0.0001). There was also a weaker but significant correlation with the citric acid content (rs 0.55, P less than 0.03). Although this may have reflected a direct effect of citric acid on Fe absorption, it should be noted that fruits containing citric acid also contained ascorbic acid (rs 0.70, P less than 0.002).(ABSTRACT TRUNCATED AT 400 WORDS)

The application of a present-day climatic model to the late quaternary in southern Africa

Abstract: A present-day climatic model is presented in which extended wet spells of near-decadal duration and dry spells of similar length are explained on the basis of surface and upper tropospheric circulation variations. Wet spells are shown to be the result of increased tropical atmospheric disturbances and tropical-temperate interaction, and to be linked to variations in the Walker Circulation. Conversely, dry spells are shown to result from diminished tropical activity over southern Africa, equatorward movement of westerly storm tracks and temperate perturbations in the westerlies. The present-day analogue is compared to preliminary spatial reconstructions of the climate of southern Africa over the last twenty-five millennia and is shown to have wide applicability in the explanation of the late-Quaternary palaeoclimates of the subcontinent. In particular, it is argued that the Last Glacial Maximum was associated with northward-displaced circulation conditions similar to those of present-day dry spells over the summer rainfall region, whereas the extensive moist conditions that prevailed for several thousand years after 9000 BP were analogous to present-day wet spell conditions with little apparent displacement of major circulation features.

Abnormalities of chromosome 12p 13 and malignant proliferation of eosinophils: a nonrandom association

Abstract: Summary. Four patients representing a spectrum of haematological malignancies are reported. Two patients had Philadelphia chromosome negative myeloproliferative disorders, one had acute lymphoblastic leukaemia and one had eosinophilic leukaemia. In each case eosinophilia was present and demonstrated to be part of the malignancy by the association of clonally abnormal metaphases with eosinophil granules. Abnormalities involving the short arm of chromosome 12 (12p 13) were a constant feature in all four cases and therefore a nonrandom association between this chromosome region and malignant eosinophil proliferation is proposed.

Hard Tissue Barrier Formation in Pulpotomized Monkey Teeth Capped with Cyanoacrylate or Calcium Hydroxide for 10 and 60 Minutes

Abstract: Monkey incisor teeth were pulpotomized in groups of 10. After physiological hemostasis, the pulps of group I were covered with isobutyl cyanoacrylate, and those of groups II and III with calcium hydroxide for 10 and 60 minutes, respectively, whereafter this compound was washed away and the wound surfaces covered with Teflon. In group IV, calcium hydroxide was used as a positive control, and Teflon as a negative control in group V. The animals were killed after 12 weeks and the teeth removed in tissue blocks. The material was processed and evaluated histologically with respect to location and continuity of a hard tissue barrier, type of newly formed hard tissue, state of the pulp, and presence of stainable bacteria in the coronal cavity. Seven of nine teeth in group I showed a hard tissue barrier. The corresponding figure for group II was eight out of 10 teeth. All teeth in groups III and IV had a barrier. The incidence of a continuous barrier increased from group I through group IV, as did the incidence of its location below the level of the original wound surface. The condition of the pulp was related to the presence of bacteria and the continuity of the barrier to the presence of inflammation. There was no bridging in group V. The results support the theory that a low-grade irritation is responsible for the formation of a hard tissue barrier in exposed pulps.

Field and laboratory investigation of Crimean-Congo haemorrhagic fever virus (Nairovirus, family Bunyaviridae) infection in birds.

Abstract: In November 1984 a case of Crimean-Congo haemorrhagic fever (CCHF) occurred in a worker who became ill after slaughtering ostriches (Struthio camelus) on a farm near Oudtshoorn in the Cape province of South Africa. The diagnosis was confirmed by isolation of CCHF virus from the patient's serum and by demonstration of a specific antibody response. It was suspected that infection was acquired either by contact with ostrich blood or by inadvertantly crushing infected Hyalomma ticks while skinning ostriches. Reversed passive haemagglutination-inhibition antibody to CCHF virus was detected in the sera of 2292 ostriches from farms in Oudtshoorn district, including 69 from the farm where the patient worked, but not in the sera of 460 birds of 37 other species. In pathogenicity studies domestic chickens proved refractory to CCHF infection, but viraemia of low intensity (maximum titre 2.5 log10 mouse ic LD50/ml) followed by a transient antibody response occurred in blue-helmeted guinea fowl (Numidia meleagris). These results offer the first direct evidence that some bird species are susceptible to CCHF virus infection.

Fanconi anemia: Another disease of unusually high prevalence in the Afrikaans population of South africa

Abstract: We have investigated the prevalence of homozygous and heterozygous Fanconi anemia (FA) in the Afrikaans community of the southern Transvaal Province. The minimum birth incidence of FA in white, Afrikaans-speaking South Africans was estimated to be 1 in 22,000, with the calculated heterozygote prevalence being approximately 1 in 77. Alternatively, based on a point prevalence of 1 in 26,000, the carrier rate may be estimated as 1 in 83. It is postulated that this unusually high frequency of the gene for FA is attributable to founder effect.

'Low-dose' corticosteroid prophylaxis against fat embolism.

Abstract: The effect of 'low-dose' corticosteroids (9 mg/kg methylprednisolone), given after skeletal trauma, on the incidence of the fat embolism syndrome and isolated arterial hypoxemia was studied in 42 controls and 40 steroid-treated subjects. Fat embolism occurred in ten controls (23.8%) and one steroid-treated subject (2.5%) (p = 0.01). A further 44 subjects developed isolated hypoxemia. This was severe (PaO2 less than 50 mm Hg) in seven of 32 controls (21.9%) and one of 39 steroid-treated subjects (2.6%) (p = 0.01). The overall incidence of hypoxemia was 67.1%, affecting 33 controls (78.6%) and 22 steroid-treated patients (55%) (p less than 0.05). The degree of hypoxemia was severe (PaO2 less than 50 mm Hg) in 12 controls (28.6%) and two (5%) of the steroid-treated subjects (p = 0.005). No control subject died or required mechanical ventilation. One steroid-treated subject without fat embolism died of a fulminant infection. Although methylprednisolone in a relatively low dose provides protection against fat embolism and pulmonary dysfunction after skeletal trauma, the safety of this therapy requires further evaluation.

Oestrogen and Progesterone Receptor Concentrations in Leiomyoma and Normal Myometrium

Abstract: The content of cytoplasmic 17 beta oestradiol and progesterone receptors in human uterine leiomyoma and normal myometrium in the Negroid population was determined. Eighteen women of reproductive age, at various stages of the menstrual cycle, were included in the study. The serum oestrogen and progesterone concentrations were also measured. This is the first report in the literature in which oestrogen and progesterone receptors in leiomyoma are significantly higher than in normal myometrium (P = 0.0002). The steroid dependence of the growth of leiomyomas may be related to the steroid receptor level. The presence of persistently high concentrations of oestrogen and progesterone receptors in leiomyoma should be helpful in the treatment of this benign tumour.

A dream of eland: An unexplored component of San shamanism and rock art

Abstract: Accounts of San (Bushman) shamanistic rock art have concentrated on the role of the trance dance in the generation of the paintings. This paper considers the role of dreaming to achieve ends similar to those served by the dance. Animal behaviour was depicted to suggest trance‐dreaming, as it was to suggest other shamanistic experiences. Sleeping eland probably represent San shamans in trance‐dreaming.

Autonomic dysfunction in severe tetanus: magnesium sulfate as an adjunct to deep sedation.

Abstract: We studied the use of continuous iv magnesium (Mg) infusion to control the sympathetic crises in a patient with severe tetanus characterized by pronounced autonomic nervous system instability. Our results suggested that Mg is a useful adjunct to the CNS depressants traditionally used. This therapy controlled the sympathetic crises and also suppressed the release of catecholamines, although Mg infusions alone appeared to be inadequate therapy.

Breast cancer in men. Clinical features, hormone receptor status, and response to therapy.

Abstract: Stage, estrogen receptor status, treatment and survival of 29 men with breast cancer attending the Breast Clinic of the Johannesburg Hospital between 1976 and 1985 are reviewed. Most patients had locoregionally advanced disease at presentation. Estrogen receptors (ER) were detected in significant concentration in 15/23 (65%). Local control was achieved in the majority, 19/26 (73%), by either surgery or radiation therapy alone or by combined modality treatment. Fifteen of 23 patients tested (65%) were ER-positive (greater than 10 fmol/mg protein). For patients with metastatic disease hormone receptor status was predictive of response to hormonal manipulation. Tamoxifen was the most acceptable and frequently used form of hormone therapy with 7/12 patients responding. Combination chemotherapy gave a response rate comparable to that seen in women with breast cancer.

Magnesium, calcium, sodium and potassium status in normotensive and hypertensive Johannesburg residents.

Abstract: Serum magnesium, calcium, sodium and potassium, and erythrocyte magnesium, sodium and potassium levels were measured in a selected group of 296 urbanised black male labourers in Johannesburg. Of these, 214 subjects were normotensive and 82 were hypertensive. The aim of the study was to examine the relationship between serum and erythrocyte electrolytes, specifically magnesium and calcium, and blood pressure in this population sample. The results showed a significant decrease in serum magnesium, calcium and potassium in the hypertensive subjects. Red blood cell magnesium was significantly lowered and red blood cell sodium was significantly raised in this group. A significant inverse correlation was found between serum magnesium and blood pressure, erythrocyte magnesium and blood pressure, serum calcium and blood pressure, and serum potassium and blood pressure. A positive correlation was observed between erythrocyte sodium and blood pressure. Of all the electrolytes assessed, magnesium (serum and erythrocyte) correlated most closely with blood pressure. The data reported here suggest that body magnesium and its interactions with calcium, sodium and potassium may, in certain groups of individuals, play an important role in the development and maintenance of high blood pressure.

Correlation of Breast Tumour Aromatase Activity and Response to Aromatase Inhibition with Aminoglutethimide

Abstract: Tumour aromatase, oestrogen (E) and progesterone (P) receptor (R) measurements were carried out in biopsies from 29 patients with advanced or recurrent breast cancer. Patients were then treated with aminoglutethimide according to one of two dosage regimens: (a) aminoglutethimide 1000 mg/day + hydrocortisone 20 mg/day, and (b) aminoglutethimide 250 mg/day. Tumour aromatase values varied from 0.05 to 2.07 pmol ER produced/mg protein/h and ER and PR values from 0.5 pmol ER produced/mg protein/h responded, whereas 0 out of 15 patients with tumour aromatase values less than this responded. Responses were seen at both dosages of aminoglutethimide. It is concluded that tumour aromatisation will be a useful measurement in predicting response to aromatase inhibitors.