Showing papers by "University of the Witwatersrand published in 1968"
Journal Article•
TL;DR: In this paper, the authors build up from the following basic facts: (i) Anyone who counts or measures is collecting statistics, and (ii) anyone who then tries to extract information from these counts and measures, is trying to analyse statistics and interpret the results.
Abstract: When trying to clarify what I mean by ""state of statistics"", I find myself building up from the following basic facts. (i) Anyone who counts or measures is collecting statistics. Anyone who then tries to extract information from these counts or measures, is trying to analyse statistics and interpret the results.
354 citations
TL;DR: The results of isotopic experiments to determine the quantities of iron lost via the gastrointestinal tract suggested a daily loss of approximately 0.1 mg. as mentioned in this paper, which was not possible to establish what proportion of this iron is reabsorbed into the body.
338 citations
TL;DR: It was found that the fracture rate in the elderly Bantu is less than one-tenth of that in Western European populations, and that males and females are affected equally.
Abstract: 1. Senile osteoporosis is one of the common causes of morbidity in old people. Its distribution in European and American populations has been deduced from epidemiological studies of its major complications, such as fractures of the vertebrae and the femoral neck. Although there has been some evidence that different population groups differ in their susceptibility to this condition, no demographic study of its prevalence in the white and Bantu races has previously been made. 2. The present paper describes an epidemiological study of femoral neck fractures in the Bantu population of Johannesburg, covering the years 1957-63. The cases were analysed by age and sex, the type of trauma and the level of the fracture. The number of fractures was related to the population at risk; the fracture incidence was expressed both as an age-specific rate and as a standardised rate and compared with fracture rates in European populations. It was found that the fracture rate in the elderly Bantu is less than one-tenth of that in Western European populations, and that males and females are affected equally. It was concluded that senile or post-menopausal osteoporosis is much less pronounced in the Bantu than in white populations. 3. The relationship of these findings to endocrine changes, calcium balance and racial factors is discussed. It is suggested that senile osteoporosis is not caused by a simple calcium deficiency but may be related to an imbalance between calcium intake, absorption and excretion, or a failure of the complex mechanism which normally controls this balance. Whatever the immediate cause, however, race plays an important part in determining the onset and distribution of the condition.
188 citations
TL;DR: Cobalt was deposited in ultra-high vacuum onto (001) copper surfaces prepared inside the vacuum chamber and the structure and lattice parameter of the cobalt remained the same as the copper until its thickness reached about 20 A. Many of these dislocations were unusual in that they were imperfect.
Abstract: Cobalt was deposited in ultra-high vacuum onto (001) copper surfaces prepared inside the vacuum chamber. If the copper substrate was at room temperature during film growth then the cobalt grew approximately as a monolayer. The structure and lattice parameter of the cobalt remained the same as the copper until its thickness reached about 20 A. At this thickness long dislocations to accommodate part of the difference between the lattice parameters of cobalt and copper were generated. Many of these dislocations were unusual in that they were imperfect. The stacking faults associated with them converted a little of the f.c.c. cobalt into the stable h.c.p. structure. If the copper was hot (350°C) during the deposition of cobalt, then film growth began with the formation of three-dimensional nuclei. Nuclei less than about 375 A in radius were f.c.c. and were strained to match the copper lattice.
146 citations
TL;DR: In this paper, an iron deposit in which there was a thickness gradient was grown in ultra-high vacuum (< 10−7 torr) on a hot (400°C) copper surface prepared inside the vacuum chamber.
Abstract: An iron deposit in which there was a thickness gradient was grown in ultra-high vacuum (< 10−7 torr) on a hot (400°C) copper surface prepared inside the vacuum chamber. Electron micrographs of the iron-copper bicrystal revealed that the growth of iron began with the generation of three-dimensional iron nuclei. These nuclei were f.c.c. and their lattices were strained to give a coherent copper-iron interface. The nuclei grew in size as the thickness of the iron increased and dislocations to accommodate part of the misfit between γ-iron and copper were generated. The dislocations were in mixed orientation and had Burgers vectors which were inclined to the iron-copper interface. A further increase in deposit thickness was accompanied by the nucleation of b.c.c. (α) iron.
115 citations
TL;DR: It is not quite certain that the mitochondria contain the entire cell complement of polyglycerolphosphatide, but evidence has been presented that purified nuclear preparations may contain significant amounts of this latter lipid.
102 citations
TL;DR: In this paper, the Transvaal and Natal Iron Age settlement revealed by aerial photography and excavation was revealed by the use of aerial images and excavation techniques, and it was described as follows:
Abstract: (1968). Transvaal and Natal Iron Age settlement revealed by aerial photography and excavation. African Studies: Vol. 27, No. 4, pp. 167-180.
74 citations
TL;DR: In this paper, the formation of en-echelon crack-arrays and feather fractures in Hospital Hill quartzites of the Lower Division of the Witwatersrand System in the Florida Hills, west of Johannesburg has been investigated.
72 citations
TL;DR: In this article, a shutter was positioned between source and substrate so that cobalt deposits in which there were thickness gradients were obtained, and examination of the thin cobalt films while they were attached to their nickel substrates revealed that they were f.c.p.
50 citations
TL;DR: The normal process of iron absorption involves several stages: iron in food is processed in the lumen of the gut to render it suitable for absorption, it then enters the niucosal cells, is passed on to the traiisferrin of plasnia, and ultimately is deposited selectively in certain tissues.
Abstract: The normal process of iron absorption involves several stages (Bothwell and Finch, 1962). Iron in food, which for the most part is complexed in organic molecules, is processed in the lumen of the gut to render it suitable for absorption. It then enters the niucosal cells, is passed on to the traiisferrin of plasnia, and ultimately is deposited selectively in certain tissues. It is helpful to consider each of these aspects individually.
47 citations
TL;DR: In this paper, the authors measured K and Rb concentrations and isotopic compositions for omphacite, diopside, garnet and mica concentrates, and whole-rocks, from mafic and ultramafic inclusions of South African kimberlite pipes and two Bavarian metamorphic eclogites.
TL;DR: Chromium films were prepared by evaporation of the metal in ultra-high vacuum onto the (001) surfaces of nickel and a shutter was moved between source and substrate during film growth so that films in which there were thickness gradients were obtained as mentioned in this paper.
Abstract: Chromium films were prepared by evaporation of the metal in ultra-high vacuum onto the (001) surfaces of nickel. A shutter was moved between source and substrate during film growth so that films in which there were thickness gradients were obtained. The very thin (roughly 10 A) parts of the chromium deposits were face-centred cubic, and dislocations to accommodate part of the misfit between the lattices of nickel and f.c.c. chromium were present. Thicker deposits contained small nuclei of chromium in the stable b.c.c. structure.
TL;DR: It would appear that anti-uveal antibody occurs not secondarily to uveal tissue damage but probably as an indication of an immunopathological aetiology.
TL;DR: In this paper, a vacuum microbalance with a sensitivity of greater than 10 −7 g and a capacity of 500 mg was used to measure the sticking coefficient of gold on NaCl single crystals under various experimental conditions.
TL;DR: Data indicate a relationship between the melanization cycle and chiasma induction: the previously postulated melanin-inducing pheromone and this chIASma- inducing phersomone are probably identical, although the latter may be a modified form of the other.
Abstract: To the two quantitative criteria for phase transformation of locusts, viz. nymphal colour and adult morphometric ratios, the change in chiasma frequencies during meiosis in the male can now be added: gregarization or swarming induces an increase in chiasma formation. The atmosphere around crowded locusts contains a pheromone which is absorbed and causes a reactive haemolymph in locust hoppers. This haemolymph may be injected into solitarious hoppers or nymphs to induce increased chiasma formation. Certain solvents like risella oil and dimethyl sulphoxide will extract the pheromone from such an atmosphere, and bio-assays with these extracts have been demonstrated to be chiasma-inducing. Such extracts are, however, not chiasma-inducing in the albino mutant, but the haemolymph from crowded normal-coloured hoppers is reactive in the albino hopper. In addition the albino mutant is solitaria-like in both morphometric ratios and chiasma frequencies. These data indicate a relationship between the melanization cycle and chiasma induction: the previously postulated melanin-inducing pheromone and this chiasma-inducing pheromone are probably identical. On the other hand, this pheromone of nymphs and the sex-maturation pheromone of adults are not identical, although the latter may be a modified form of the other.
TL;DR: In vivo incorporation of 14C-6-orotic acid in different nuclear fractions was measured and it was shown that the diploid and tetraploid parenchymal nuclei had the same specific radioactivity whereas the stromaluclei were only about 10 per cent as active.
TL;DR: In this article, the authors studied the characteristics of the mountain wind in the Bushmans valley of the Drakensberg and showed that the maximum contribution to total turbulent energy occurs in surges with periods 1-4 hours.
Abstract: The mountain wind in the Bushmans valley of the Drakensberg is shown to have distinctive spatial and temporal characteristics. The onset of the wind occurs as a pronounced surge of cool air. Thereafter surging continues as regular fluctuations in turbulent energy occur throughout the 12- to 15-hour period of the mountain wind. Horizontal velocity spectra show that the maximum contribution to total turbulent energy occurs in surges with periods 1-4 hours. A two-parameter parabolic model best describes the mean mountain wind profile. Departures from this profile may be pronounced during surges. The anti-mountain wind is shown to exhibit a regular parabolic variation of velocity with height on a number of occasions despite the lack of any topographic control at the height of its occurrence. Dissipation of the mountain winds is discussed and a model of nocturnal local winds in the Drakensberg foothills is presented.
TL;DR: In this article, the epitaxial growtj of CdS, ZnS and HgS on platelet substrates has been studied and two types of growth island were observed, namely round islands and faceted islands.
TL;DR: Fractographic studies by optical microscopy have been carried out on WC-Co alloys fractured in bending tests as mentioned in this paper, and plastic deformation has been found to precede, accompany and follow fracture, at least on a microscopic scale.
01 Feb 1968
Journal Article•
TL;DR: In this article, an epidemiological study of femoral neck fractures in the Bantu population of Johannesburg, covering the years 1957-63, was carried out and it was concluded that senile or post-menopausal osteoporosis is much less pronounced in the bantu than in white populations.
Abstract: 1. Senile osteoporosis is one of the common causes of morbidity in old people. Its distribution in European and American populations has been deduced from epidemiological studies of its major complications, such as fractures of the vertebrae and the femoral neck. Although there has been some evidence that different population groups differ in their susceptibility to this condition, no demographic study of its prevalence in the white and Bantu races has previously been made. 2. The present paper describes an epidemiological study of femoral neck fractures in the Bantu population of Johannesburg, covering the years 1957-63. The cases were analysed by age and sex, the type of trauma and the level of the fracture. The number of fractures was related to the population at risk; the fracture incidence was expressed both as an age-specific rate and as a standardised rate and compared with fracture rates in European populations. It was found that the fracture rate in the elderly Bantu is less than one-tenth of that in Western European populations, and that males and females are affected equally. It was concluded that senile or post-menopausal osteoporosis is much less pronounced in the Bantu than in white populations. 3. The relationship of these findings to endocrine changes, calcium balance and racial factors is discussed. It is suggested that senile osteoporosis is not caused by a simple calcium deficiency but may be related to an imbalance between calcium intake, absorption and excretion, or a failure of the complex mechanism which normally controls this balance. Whatever the immediate cause, however, race plays an important part in determining the onset and distribution of the condition.
TL;DR: In this paper, CdS and ZnS platelets were grown using the gas transport technique, and the surfaces exhibited striations and steps Dislocations were observed in the platelets.
TL;DR: In this article, the synthesis of derivatives of 5-deoxy-5-thio-d-xylose was described. But the synthesis was performed using methanolysis.
Journal Article•
TL;DR: In this paper, the observed behaviour of the sticking coefficient of Au on uncontaminated (thermally etched) NaCl1) is approximated in terms of a stepped surface model which, when fitted to the experimental results, gives a step spacing of 734 A in fair agreement with the spacings observed on electron micrographs of very thin (∼20 A) Au films grown on such NaCl surfaces.
TL;DR: In this paper, the meaning of a trait adjective may be stated by denying the opposite of the adjective, and two hundred sixty-four Ss were divided into two groups, adjectives defined by the F group being favorable-seeming, and those by the U group unfavorable-seemed.
31 Oct 1968
TL;DR: In this article, the effective charge on the Group III or Group II ion increases, and the stable structure changes from the sphalerite to the wurtzite structure.
Abstract: The structures of the III–V and II–VI compounds are discussed with respect to the effective charges on the ions. It is shown that as the effective charge on the Group III or Group II ion increases, the stable structure changes from the sphalerite to the wurtzite structure.
TL;DR: In this paper, the authors measured the sticking coefficient of gold on KCl single crystals under various experimental conditions and showed that a relatively high sticking coefficient generally accompanies epitaxial growth although the reverse is not true in general.