Showing papers by "University of the Witwatersrand published in 1971"

Immediate effects of intravenous verapamil on atrial fibrillation.

Abstract: The immediate effects of intravenous verapamil in 20 cases of atrial fibrillation are reported. There are two main effects (1) verapamil causes a marked slowing of the ventricular rate. (2) Verapamil regularizes the ventricular rhythm by stabilizing A-V conduction. The conduction of the fibrillation impulses results in regular ventricular rhythm.

Violent deformation of rock near deep-level, tabular excavations—seismic events

Abstract: Inelastic deformation of the rock near the edges of the thin tabular excavations (stopes) of deep-level mines sometimes occurs violently, resulting in a seismic event. These seismic events are produced in the highly-stressed rock near the edges of the stopes and appear to be the result of shear failure across a plane; these conclusions are based on seismic as well as underground observations. The seismic events occurring near stopes can be described using a model based on the theory of dislocations; they result from two edge dislocations of opposite sign annihilating each other and releasing energy. The instantaneous convergence of the stope that is observed to occur at the time of a large mine tremor is compatible with the observed seismic energy of the tremor, according to analysis based on the dislocation model.

Some factors affecting the release of iron from reticuloendothelial cells.

Abstract: Summary. Factors modifying the release of iron from reticuloendothelial cells were studied in rats by injecting heat-denatured erythrocytes containing [59Fe]haemoglobin. The cells were rapidly taken up by the liver and spleen, and a proportion of the 59Fe was released into the plasma, the maximum rate being between 1 and 4 hr after injection. The remaining 59Fe was incorporated into storage compounds. A 10-fold variation in the load of denatured erythrocytes produced a proportional change in the amount of iron released, the percentage remaining constant. Percentage release of 59Fe was enhanced in venesected rats and diminished in hypertransfused rats. Release was inhibited by injecting either unlabelled denatured erythrocytes or iron bound with nitrilotriacetic acid (NTA-iron) before the 59Fe-labelled cells, the maximum effect being obtained if the interval between the two injections was 3-9 hr. Release was also inhibited by injecting NTA-iron 30 min after the denatured labelled erythrocytes. Inhibition was always preceded by a rise in the serum-iron concentration, and was associated with an increase in the percentage of 59Fe incorporated into ferritin. It is postulated that the shortage of free transferrin binding sites for iron delays the entry of liberated haemoglobin iron into the plasma, and consequently there is enlargement of a ‘pre-release’ iron pool. Other workers have shown that iron induces the synthesis of ferritin; the presence of a stimulated mechanism for ferritin synthesis within the reticuloendothelial cells would result in the diversion of an increased percentage of erythrocyte iron into storage compounds.

Sulfur Isotopes in Swaziland System Barites and the Evolution of the Earth's Atmosphere.

Abstract: Sedimentary barites from the Swaziland System of South Africa (more than 3000 million years old) have sulfur-34 ratios that are enriched by only 2.5 per mil with respect to contemporary sulfides. To explain this small fractionation, it is proposed that oxygen pressure in the earth's atmosphere was very low and that local oxidation occurred in a photosynthetic layer of the ocean.

Ferromagnetism in epitaxial F.C.C. iron films

Abstract: Thin iron films, ∼ 30 A thick, have been grown on (110) copper single crystal substrates. The structure of the films was examined by reflection electron diffraction and found to be f.c.c. in parallel orientation with the copper substrate. The specimens were examined by electron spin resonance and found to be ferromagnetic.

Human skeletal remains from the Cave of Hearths, Makapansgat, Northern Transvaal.

Abstract: A detailed study has been made of the oldest South African Upper Pleistocene hominid remains found in Acheulian context in a well-stratified sealed cave deposit, the Cave of Hearths, Makapansgat, Northern Transvaal. Possibly 55,000 years of age, the remains comprise a juvenile right mandibular body with teeth, and part of a right radius. The mandible is highly robust, markedly prognathous, has a slight to moderate bony chin, an appreciable planum alveolare, a low supraspinous foramen, large alveolar part with big tooth roots, parallel upper and lower borders, a superior transverse torus and poorly developed genial apophysis. The teeth are fairly large, narrow and elongate; M2 is smaller than M1; both molars have a +5 cusp pattern, and the first molar shows moderate taurodontism. There is good evidence that the jaw shows congenital lack of M3: after the Chinese Lantian jaw, this is the second oldest hominid mandible and the first African fossil man with this feature. The radius has a relatively large head atop a disproportionately narrow neck; marked angulation of neck on shaft; and a strongly developed bicipital tubercle. The remains show a cluster of features which ally them with African Neandertaloids and earlier hominids of N.W. Africa. These geographically widespread African remains may represent a transitional population between H. erectus and H. sapiens neanderthalensis. This population has been called by Campbell, this author and others H. sapiens rhodesiensis (after the first-discovered specimen from Broken Hill): to this taxon the Cave of Hearths bones are tentatively assigned.

The diagnostic and prognostic significance of the serum enzyme changes in heatstroke

Abstract: Serum transaminase (SGOT, SGPT), lactic dehydrogenase (LDH) and creatine phosphokinase (CPK) levels were measured serially in 84 Bantu gold-miners with a provisional diagnosis of heatstroke. In 75 patients proved to have heatstroke, SGOT levels were invariably, and SGPT, LDH and CPK values almost invariably, elevated within 24 hours of admission. The levels continued to rise for approximately 48 hours and remained elevated for average periods of 12 to 14 days. In the patients who proved to have acute infections, SGOT, SGPT and LDH values were normal. The serum enzyme changes were therefore useful in confirming or excluding the diagnosis of heatstroke. The degree of elevation of the enzyme levels was also a reliable index of the severity of tissue damage in heatstroke and hence the patient's likely outcome. In 15 patients in whom the SGOT level exceeded 1,000 units in the first 24 hours, renal, hepatic and cerebral damage tended to be severe, and death or permanent sequelae were common. In 20 patients with SGOT values of less than 1,000 units, the tissue injury was usually mild or moderate and completely reversible, and there was only 1 death.

Velocity and turbulence measurements of air flow through a packed bed

Abstract: Mean velocity and turbulence measurements in the void spaces of a cubic packing of equal spheres have been made at Reynolds numbers of 27,000, 10,000, 5,000 and 2,500, where NRe is based on superficial air velocity and a sphere diameter of 7 cm. Two cubic arrangements were used: in the regular arrangement, the mean flow was parallel to one of the principal axes, while in the skewed arrangement, the mean flow made equal angles with the three principal axes of the packing. Transverse mean velocity and turbulence intensity profiles across the center line of a central pore have been measured behind every bank and behind the bed for the regular arrangement of ten banks of spheres. The power spectrum and probability distribution of the fluctuating velocity have also been determined.

The effect of siderosis and ascorbic acid depletion on bone metabolism, with special reference to osteoporosis in the Bantu

Abstract: 1. There is an association between iron overload, ascorbic acid deficiency and osteoporosis in middle-aged South African Bantu males. The iron overload contributes to the ascorbic acid deficiency by accelerating its oxidative catabolism. The object of the present investigation was to explore the possibility that the osteoporosis results from chronic ascorbic acid deficiency.2. On quantitative microradiography, percentage bone-formation surface was normal but percentage bone-resorption surface was significantly increased in ten osteoporotic subjects compared with seven control subjects.3. There was a significant inverse correlation between bone mineral density and liver storage iron concentration in thirty-five Bantu subjects. In thirteen individuals aged 39 years or less, liver storage iron concentration was significantly correlated with percentage bone-resorption surface.4. Guinea-pigs deprived of ascorbic acid for 21 d exhibited both significantly diminished percentage bone-formation surface and increased percentage bone-resorption surface.5. Guinea-pigs overloaded with iron by injections of iron dextran developed significantly reduced hepatic ascorbic acid concentrations and bone mineral densities; percentage bone-formation surface was significantly diminished and percentage bone-resorption surface significantly increased. Ascorbic acid injection largely prevented the bone changes.

The Ceres, South Africa, earthquake of September 29, 1969: I. Report on some aftershocks

Abstract: Aftershocks following the Ceres earthquake of September 29, 1969, (Magnitude 6.3) were monitored using a number of portable seismic recording stations. Earthquakes of this magnitude are rare in South Africa. The event occurred in a relatively densely-populated part of the Republic, and resulted in nine deaths and considerable damage. Accurate locations of some 125 aftershocks delineate a linear, almost vertical fault plane. The volume of the aftershock region is 3 × 9 × 20 km 3 with the depth of the aftershocks varying from surface to 9 km. Aftershocks following the September event had almost ceased when another large earthquake (Magnitude 5.7) occurred on April 14, 1970. Following this event, the frequency and magnitude of aftershocks increased, and they were located on a limited portion of the same fault system delineated by the September 29th aftershocks. Previously-mapped faults do not correlate simply with the fault zone indicated by the aftershock sequence.

Optimal Disaggregation of Aggregate Production Plans

Abstract: Aggregate Production Planning APP is concerned with a minimum cost adaptation of some production process to demand fluctuations, by means of controlling overall production rate P and workforce size W. Disaggregation aims at allocating P and W to individual products such that an optimal sales program is obtained. A technique is developed which may be used for disaggregation when product contributions are nonlinear. It relies on decreasing marginal contributions as an evaluation criterion. In conjunction with an APP model, the technique can be used for a simultaneous derivation of aggregate and disaggregate decisions. This is illustrated by an application to a hypothetical production and sales planning problem.

Spatial variation of rainfall spectra in south africa

Abstract: Fourier and spectral analysis of rainfall records at 163 South African stations over the period 1910–1969, and at thirty-nine stations from 1880–1969, shows that cyclical fluctuations with periods of about 18–20, 13–15, 10, 45, 35, 28, and 23 years account for much of the observed rainfall variance over the country These fluctuations exhibit distinctive regional distributions that appear to have changed little over the last century

Free Overall as Flow Measuring Device

Abstract: The critical depth in a rectangular channel gives a simple depth-discharge relation. However, the location of the critical depth cannot be easily determined. Herein, a functional relationship between the critical depth and the end depth, which can readily be measured, is presented.

Observations on Some Valley Forms and Deposits in the Sani Pass Area, Lesotho

Abstract: Deposits located in hollows, reminiscent of nivation cirques and restricted to altitudes over 2 900 m, are described form an area south of Sani Pass. The deposits consist of layers of gravel with and without boulders, alternating with organic clays. It is postulated that these deposits provide evidence of former climatic fluctuations.

Muons Produced By Atmospheric Neutrinos: Experiment

Abstract: The interaction of high-energy muon neutrinos produced in the atmosphere by primary cosmic rays has been observed deep underground (8.74\ifmmode\times\else\texttimes\fi{}${10}^{5}$ g ${\mathrm{cm}}^{\ensuremath{-}2}$ std. rock) in the rock surrounding a large-area (160 ${\mathrm{m}}^{2}$) liquid-scintillation-detector hodoscope. A series of arguments is given to separate the residual atmospheric muons which reached the detector from those produced by neutrino interactions in the surrounding rock. These arguments are based on the widely differing angular distributions and mean energies of the two sources. The observation of four events arising from the decay of muons stopping in the detector suggests that the energy of neutrino-induced muons is \ensuremath{\sim}\textonehalf{} GeV. Operation of the system over a three-year period yielded a total of 39 which we identify as neutrino-produced muons. Of these, 35 were in the aperture chosen for the observation of neutrino-induced muons, yielding a total rate of (6.5\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. In a companion paper, this result is compared with rates predicted using various theoretical models of the neutrino-nucleon interaction. This comparison selects the most appropriate model and leads to an underground neutrino-induced muon flux. In the present paper the simplifying approximation of an isotropic neutrino distribution leads directly to a flux of (3.7\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ ${\mathrm{sr}}^{\ensuremath{-}1}$.

Evidence for intermediate structure near an isobaric analog resonance.

Abstract: In an investigation of the elastic and inelastic scattering of protons on separated isotopes of 70Ge and 72Ge for the purpose of locating isobaric analogue states of 71Ge and 73Ge in 71As and 73As, respectively, we found one l=0 resonance in each isotope, displaying pronounced structure within their “widths”. The purpose of this Contribution is to present evidence that this structure is intermediate between the gross analogue resonance structure on the one hand, and the ultimate compound-nucleus fine structure on the other hand. It will also be argued that these structures are not Ericson fluctuations.

Presence and Function of Disclinations in Surface Coats of Unicellular Organisms

Abstract: IF a cell which is topologically a sphere is covered with a coat composed of identical units arranged to form a surface crystal, this crystal necessarily1 contains screw disclinations of total strength +2 complete rotations. Harris and Scriven2 draw attention to the micrograph of a marine bacterium, Nitrosomonas, published by Watson and Remsen3, on the cover of Science, showing a coat of apparently spherical units in close packing. They say that intrinsic disclinations are strongly indicated. We have undertaken further analysis of the disclination structure of this coat.

On the Bounds of the Range of Order Statistics

Abstract: Let x1x2 ··· xn be any set of number satisfying Σ xi=0 Σ xi 2=1. There are bounds on the range of xi when the set {xi} is ranked (a) by x1≥x2≥ ··· ≥ xn and (b) by |x1|≥|x2|≥ ··· ≥|xn|. These bounds are given. The applicability to finite populotionr is pointed out.

Mangroves on Aldabra

Abstract: Mangrove trees grow only on sheltered coasts, hence on Aldabra they occur along the shores of the lagoon. In these mangrove communities four species are common and were found in each locality visited. These are Avicennia marina (Forsk.) Vierh., Bruguiera gymnorhiza (L.) Lam., Ceriops tagal (Perr.) C.B. Rob., and Rhizophora mucronata Lam. In a few localities only, these are accompanied by one or other of Lumnitzera racemosa Willd., Sonneratia albaj. Sm., or Xylocarpus granatum Koen. The fern Acrostichum aureum L. is abundant on Aldabra, sometimes in association with mangroves but more commonly among the maritime scrub where it tends to occur in crevices and solution holes at a slightly lower level than the trees and shrubs of the scrub. Mangroves occur almost all round the lagoon shores, more commonly in some places than in others, more luxuriantly in some places than in others. Along only a few rocky stretches of the lagoon shores are they absent. Nowhere on the island is there a complete pattern of the zonation described for other Indian Ocean shores by Macnae (1968). On Aldabra the landward fringe is well developed only in one locality and the seaward fringes have rarely developed.

Low molecular weight dextran in the treatment of livedo reticularis with ulceration

Abstract: SUMMARY Six cases of livedo reticularis with ulceration were treated with large amounts of low molecular weight dextran. The lesions healed well with this therapy, and subsequent relapses have been less frequent and easier to control. The method of administration is outlined and a possible explanation for the prolonged beneficial effect is advanced.