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Showing papers by "University of the Witwatersrand published in 1977"


Journal ArticleDOI
TL;DR: The fast generation of discrete random variables with arbitrary frequency distributions is discussed, related to rejection techniques but differs from them in that all samples comprising the input data contribute to the samples in the target distribution.
Abstract: The fast generation of discrete random variables with arbitrary frequency distributions is discussed. The proposed method is related to rejection techniques but differs from them in that all samples comprising the input data contribute to the samples in the target distribution. The software implementation of the method requires at most two memory references and a comparison. The method features good accuracy and modest storage requirements. I t is particularly useful in small computers with limited memory capacity.

553 citations


Journal ArticleDOI
TL;DR: In this paper, a possible alternative to the hypothesis that the sequence X 1, X 2, X 3, X 4, X 5, X 6, X 7, X 8, X 9, X 10, X 11, X 12, X 13, X 14, X 15, X 16, X 17, X 18, X 19, X 20, X 21, X 22, X 23, X 24, X 25, X 26, X 27, X 28, X 29, X 30, X
Abstract: A possible alternative to the hypothesis that the sequence X 1, X 2, …, Xn are iid N(ξ, σ2) random variables is that at some unknown instant the expectation ξ shifts. The likelihood ratio test for the alternative of a location shift is studied and its distribution under the null hypothesis found. Tables of standard fractiles are given, along with asymptotic results.

328 citations


Journal ArticleDOI
TL;DR: The pattern of pacesetter potenitals in patients with gastric ulcer, gastric cancer, and duodenal ulcer was similar to that of patients without such diseases, providing further evidence that both are myogenic phenomena.
Abstract: Gastric electrical activity was recorded from twenty-six patients at celiotomy. The human gastric pacemaker was localized to an area in the midcorpus along the greater curve. Pacesetter potentials were generated regularly by the pacemaker at a mean frequency of 3.2 cycles/min and were propagated circumferentially and aborally from the pacemaker, increasing in amplitude and velocity as they approached the pylorus. The pattern of pacesetter potentials in patients with gastric ulcer, gastric cancer, and duodenal ulcer was similar to that of patients without such diseases. Complete transection of the gastric corpus isolated the distal stomach from the natural pacemaker and resulted in the appearance of a new pacemaker in the distal stomach with a slower frequency. The fact that proximal gastric vagotomy did not greatly alter the frequency of generation or the pattern of propagation of the pacesetter potential provided further evidence that both are myogenic phenomena.

275 citations


Journal ArticleDOI
27 Jan 1977-Nature
TL;DR: The new find supports the view that the Sterkfontein toolmaker was not the earlier A. africanus, but a later hominid related to Homo habilis, and is establishing indisputably the provenance of the specimen.
Abstract: A skull with numerous Homo features was discovered at Sterkfontein, near Krugersdorp, Transvaal, in August 1976. It stems from member 5 of the Sterkfontein Formation, with stone tools and with fauna pointing to an age of 2.0–1.5 Myr. The underlying member 4 contains Australopithecus africanus, no stone tools, and fauna dated 3.0–2.5 Myr. The new find supports the view that the Sterkfontein toolmaker was not the earlier A. africanus, but a later hominid related to Homo habilis. By a remarkable double coincidence, the first pieces of the new skull, Stw 53, were found on August 9, 1976, 40 years to the day after Robert Broom's first visit to Sterkfontein, while the last part came to light on August 17, the 40th anniversary of Broom's first discovery of a hominid cranium at Sterkfontein. Although most of the fragments were found in a decalcified pocket of cave earth, one large part of the calvaria was still present in the calcified wall of the pocket, thus establishing indisputably the provenance of the specimen.

131 citations


Journal ArticleDOI
TL;DR: In this paper, major and trace element and modal analyses are presented for unaltered, epidotized, and carbonated tholeiite flows from the Barberton greenstone belt.
Abstract: Major and trace element and modal analyses are presented for unaltered, epidotized, and carbonated tholeiite flows from the Barberton greenstone belt. Au, As, Sb, Sr, Fe+3, Ca, Br, Ga, and U are enriched and H2O, Na, Mg, Fe+2, K, Rb, Ba, Si, Ti, P, Ni, Cs, Zn, Nb, Cu, Zr, and Co are depleted during epidotization. CO2, H2O, Fe+2, Ti, Zn, Y, Nb, Ga, Ta, and light REE are enriched and Na, Sr, Cr, Ba, Fe+3, Ca, Cs, Sb, Au, Mn, and U are depleted during carbonization-chloritization. The elements least affected by epidotization are Hf, Ta, Sc, Cr, Th, and REE; those least affected by carbonization-chloritization are Hf, Ni, Co, Zr, Th, and heavy REE. Both alteration processes can significantly change major element concentrations (and ratios) and hence caution should be used in distinguishing tholeiites from komatiites based on major elements alone. The amount of variation of many of the least mobile trace elements in the altered flows is approximately the same as allowed by magma model calculations. Hence, up to about 10% carbonization and 60% epidotization of tholeiite do not appreciably affect the interpretation of trace-element models for magma generation.

101 citations


Journal ArticleDOI
TL;DR: An alternative variational formulation of Vlasov's two parameter foundation model is presented in this paper, which provides a rigorous theoretical basis for the present form of the vertical deformation profiles.

99 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the lead isotope ratios of kimberlites and autoliths in the Cretaceous and found a large spread in initial lead ratios.

98 citations


Journal ArticleDOI
TL;DR: Dietary history shows that the urbanization of the South African black has been accompanied by the emergence of diverticular disease, a condition higher to virtually nonexistent in this population.

98 citations


Journal ArticleDOI
TL;DR: Peripheral electrical stimulation of the rat produced a "dose-dependent" analgesia both in intact and in spinal animals, and Naloxone, a narcotic antagonist, almost completely reversed this analgesia.

96 citations


Journal ArticleDOI
TL;DR: Ascorbic acid is capable of improving Fe absorption from a cereal source and can partially overcome the inhibitory effect of tea and might be expected to facilitate the absorption of at least some forms of Fe that may contaminate food.
Abstract: 1. The feasibility of improving iron nutrition by fortifying cane sugar with ascorbic acid was studied. 2. The absorption of Fe added to maize-weal porridge was measured in 116 volunteer multiparous Indian women using the radio-Fe erythrocyte utilization method. The meals were fed with and without tea or coffee and with and without varying amounts of ascorbic acid. 3. The mean absorption of Fe from maize-meal porridge was very low (3.8 %), being even further reduced (2.1 %) when tea was drunk with the meal. 4. The addition of 50 or 100 mg ascorbic acid to maize-meal porridge caused approximately a 10-fold increase in Fe absorption. The increase was much less when tea was present, being 2-fold and 5-fold with 50 and 100 mg ascorbic acid respectively. The inhibitory effect of tea on Fe absorption could, however, be overcome by giving larger doses of ascorbic acid (250 and 500 mg). 5. When contaminating Fe (2.5 mg) in the form of labelled rust (Fe,O,) or ferric hydroxide was added to maize-meal porridge it was poorly absorbed (mean values were 0.01 % and 1.5 % respectively). The addition of 100 mg ascorbic acid increased the mean Fe absorption rates to 0.5 % and 6.7 %with Fep03 and Fe(OH), respectively. Fe(OH), was found to be absorbed about half as well as the intrinsic Fe present in maize-meal porridge. 6. It is concluded that ascorbic acid is capable of improving Fe absorption from a cereal source. It can partially overcome the inhibitory effect of tea and might be expected to facilitate the absorption of at least some forms of Fe that may contaminate food. Current methods aimed at promoting adequate iron nutrition in communities that are at risk of Fe deficiency have relied on the fortification of dietary staples with added Fe. How

87 citations


Journal ArticleDOI
TL;DR: The correct precaution would be to prohibit the race in circumstances in which an occurrence might be expected-a moisture laden atmosphere, a following wind and the early afternoon of a day with a shade temperature of 85” F (29.Y C) or higher.
Abstract: I am of the opinion that in healthy subjects the only serious potential risk to life from violent exercise is heat stroke-a danger well exhibited by examples I have seen of alarming collapse and, on one occasion, death. The correct precaution would be to prohibit the race in circumstances in which an occurrence might be expected-a moisture laden atmosphere, a following wind and the early afternoon of a day with a shade temperature of 85” F (29.Y C) or higher.

Journal ArticleDOI
01 Oct 1977-Nature
TL;DR: In this article, the authors describe a group of lineations recently mapped in the Antarctic Basin off Dronning Maud Land, interpreted as being due to sea floor generated at the South-west Indian Ocean Ridge in the Early Cretaceous, where transform fault traces have been extended for more than 100 km from the spreading centre and where magnetic lineations have been related to the present tectonic pattern.
Abstract: THE accreting margin between the African and Antarctic plates is now well understood between the Bouvet triple junction and Marion Island (Fig. 1). Published data obtained from the ridge axis near 1°W1, 15°E2, and 36°E3 can be combined to yield a relative rotation pole at 11°N, 41°W with an equatorial half spreading rate of 0.8 cm yr−1. Away from the spreading axis, very little is known apart from a narrow region to the north in the Mozambique Basin where Bergh and Norton3 have shown that the present spreading regime commenced at least as far back as the Late Cretaceous. This is the only region where transform fault traces have been extended for more than 100 km from the spreading centre and where magnetic lineations have been related to the present tectonic pattern. I describe here a group of lineations recently mapped in the Antarctic Basin off Dronning Maud Land, interpreted as being due to sea floor generated at the South-west Indian Ocean Ridge in the Early Cretaceous.

Journal ArticleDOI
TL;DR: A hypothesis is presented whereby the rate of influx of orthophosphate into the root cortical cells is regulated by the turn-over rate of the pool of inorganic phosphate in the cytoplasm, and by the rateof transport of in organic phosphate to the shoot.
Abstract: The effect of Al and P on the growth of lucerne (Medicago sativa) was studied in nutrient solutions in which aluminium phosphate did not precipitate. Al and P retained in the free space of the roots was washed out with 0.1N HCl/O4 at 5°C. The inhibitory effect of Al on growth was much less at pH 5 than at pH 4.5, although 3 to 4 times as much Al was found in the roots and shoots of the pH 5 plants. It is suggested that the low toxicity of high contents of Al was due to a portion of the uptake at pH 5 being in the form of polymeric aluminophosphate complexes of low net charge density. The optimum pH for the formation and polymerization of such complexes is around 5, and their composition depends on the P/Al mole ratio of the initial solutions. Washing32P-labelled roots in unlabelled P solutions containing Ca showed that 12–43 per cent more of the total label diffused out of the Al-treated roots at pH 5 than from control roots. This was consistent with estimates by solution analysis of 16–36 per cent (depending on the P/Al mole ratio) of the P present in the original uptake solutions being complexed with Al.

Journal ArticleDOI
TL;DR: While the free-living heterotrophic Dinophyceae comprise the largest proportion of the class they have been, by far, the most poorly studied at the fine structural level.
Abstract: Nutritionally, there are three basic types of Dinophyceae: (1) free-living photosynthetic autotrophs; (2) parasitic heterotrophs living on or in other organanisms and (3) free-living phagocytic or chemosynthetic heterotrophs. Representatives of the first type, the free-living photosynthetic autotrophic species, have been extensively investigated at the fine-structural level (for a review see Dodge, 1971). There are fewer species of the second type, the parasitic Dinophyceae, but many of these have been investigated in the electron microscope (Cachon & Cachon, 1966, 1970, 1971a, b ; Cachon et al. 1968; Soyer, 1969 c; Manier, Fize & Grizel, 1971; Siebert & West, 1974). The third type, the free-living heterotrophic Dinophyceae, probably comprises the greatest number of species in the class; as Kofoid & Swezy (1921) state ‘One cannot work with the marine unarmored Dinoflagellata for even a short time without being struck by the fact that the majority of the individuals observed show evidence of holozoic nutrition and that the number actually containing chromatophores is relatively small throughout the entire Dinoflagella’. While the free-living heterotrophic Dinophyceae comprise the largest proportion of the class they have been, by far, the most poorly studied at the fine structural level. Investigations on these organisms have been limited to a comprehensive study of Oxyrrhis marina (Dodge & Crawford, 1971a, b , 1974) plus studies on specific parts of Cryptothecodinium cohnii (Kubai & Ris, 1969; Pokorny & Gold, 1973) and Noctiluca miliaris (Afzelius, 1963; Soyer, 1968, 1969a, b ; Zingmark, 1970).

Journal ArticleDOI
TL;DR: In this article, a palaeoenvironmental synthesis of the facies relationships indicates that back-barrier tidal flats occurred lateral to a non-barred estuary, and two subfacies are recognized within the medium-to-fine-grained sandstones.

Journal ArticleDOI
TL;DR: By fitting a trigonometrical regression model to a regionally averaged time series for the period 1910-72, and by extrapolation to the year 2000, an estimate of future extended wet and dry spells has been made for the summer rainfall region of South Africa as mentioned in this paper.
Abstract: By fitting a trigonometrical regression model to a regionally averaged time series for the period 1910–72, and by extrapolation to the year 2000, an estimate of future extended wet and dry spells has been made for the summer rainfall region of South Africa. It is suggested that the periods 1972–81 and 1991–2000 will experience above normal rainfall and the period 1981–90 will be drier than normal. Results to date show that mean regional rainfall for the hydrological years 1972–73 to 1975–76 has conformed to the suggested pattern.

Journal ArticleDOI
01 Oct 1977-Hand
TL;DR: A new method of tendon suture has been designed to eliminate the development of a gap when tension is applied to the repair and has been demonstrated to resist distraction at relatively high tensions on cadaveric tendon.
Abstract: A new method of tendon suture has been designed to eliminate the development of a gap when tension is applied to the repair. It has been demonstrated to resist distraction at relatively high tensions on cadaveric tendon. The possible advantages of the technique are discussed.

Journal ArticleDOI
01 Nov 1977-Urology
TL;DR: Most lymphoceles may be managed conservatively initially, however, if surgery is required, open drainage and packing would appear to be the most reliable procedure.

Journal ArticleDOI
TL;DR: In this paper, measurements of equilibrium phosphate concentrations, adsorbed phosphate and isotopically exchangeable phosphate (Et) were made on suspensions of acid soils at initial P concentrations ranging from 1-1000 μM and pH values between 4.2 and 6.8.
Abstract: Summary Measurements of equilibrium phosphate concentrations, adsorbed phosphate and isotopically exchangeable phosphate (Et) were made on suspensions of acid soils at initial P concentrations ranging from 1–1000 μM and pH values between 4.2 and 6.8. At low P concentrations (1–100 μM), the affinity of the adsorption reaction was greatest at pH 5.2–5.5. This result, which was inconsistent with the ligand-exchange hypothesis of Kingston et al. (1967, 1972, 1974), was interpreted in terms of the formation of basic aluminium phosphates of varying composition that depended on the OH/P ratio in solution. At the highest P concentrations (1000 μM), when the affinity of adsorption was least at pH 5.2–5.5, it appeared that basic calcium phosphates were precipitating at pH values > 5.5. In suspensions containing 1–100 μM P initially, values of Et did not change consonantly with values of adsorbed P over the pH range 4.8 to 5.5. It is suggested that the Et values were underestimated due to the presence of labelled complexes in solution which were detected by scintillation counting but not by the analysis for orthophos-phate. Evidence from solution studies (White et al., 1976) suggested that as much as one-third of the phosphate could be complexed with aluminium in solutions between pH 4.7 and 5.4 at P/A1 mole ratios of 0.075 to 7.5. It was apparent that the interpretation of the physical significance of E values in acid soils is complex and requires careful appraisal of the experimental techniques used.

Journal ArticleDOI
TL;DR: It is suggested that in porphyria variegata a dominantly inherited structural gene mutation results in an active ferrochelatase whereas in protoporphyria the genetic mutationresults in an unstable ferroChelatase.
Abstract: Erythroid ferrochelatase activity has been studied in the normoblasts of patients with porphyria variegata and protoporphyria. Two methods were used for the investigation: one using intact cells and the other lysed cells, each measuring the amount of haem synthesized by normoblasts. In patients with porphyria variegata, ferrochelatase activity estimated by both methods was approximately 50% of the normal, and in protoporphyria the ferrochelatase activity was normal in intact normoblasts but was 20% of the normal in sonicated normoblasts (marrow lysates). It is suggested therefore that in porphyria variegata a dominantly inherited structural gene mutation results in an active ferrochelatase whereas in protoporphyria the genetic mutation results in an unstable ferrochelatase. The mechanism of the enzyme instability is not known though a number of postulates are discussed.

Journal ArticleDOI
TL;DR: A new class, the Haptophyceae, is erected to contain the two orders of the Isochrysidales and Prymnesiales, both of which differ from other chrysomonads in that the two true flag-ella are smooth with no coarse hairs (‘mastigonemes’) and that the third appendage found in genera of the latter order is a unique structure.
Abstract: The order Isochrysidales was erected by Pascher in 1910 to accommodate chrysomonads with two equal flagella. It was based on the family Hymenomonadaceae (Senn, 1900) and included such genera as Synura Ehrenberg (later shown to be heterokont and therefore incorrectly placed here; Hovasse, 1949; Manton, 1955), Wyssotzkia Lemmermann and Hymenomonas Stein. Papenfuss (1955) used the name in a similar sense but encompassing also the coccolithophorids, while those genera with two equal flagella and a ‘short third flagellum’ ((Prymnesium Massart, Platychrysis N. Carter, Chrysochromulina Lackey) were placed in the order Prymnesiales. Subsequently it was demonstrated that members of the Isochrysidales and Prymnesiales differ from other chrysomonads in that the two true flag-ella are smooth with no coarse hairs (‘mastigonemes’) and that the third appendage found in genera of the latter order is a unique structure, termed the ‘haptonema’ by Parke, Manton & Clarke (1955). On the basis of these observations, Christensen (1962) erected a new class, the Haptophyceae (now referred to by the typified name Prymnesiophyceae; Hibberd, 1976 a), to contain the two orders although Bourrelly (1968) preferred to retain them within the Chrysophyceae whilst recognizing their unique status by the erection of a sub-class, the Isochrysophycidae.

Journal ArticleDOI
TL;DR: In this article, the spatial and point characteristics of mean non-surface inversions by season and by month were investigated for the years 1969-1972, and the nature of inversion occurrence within six layers of the lower atmosphere.
Abstract: Radiosonde data for the years 1969–1972 have been processed to determine non-surface inversion conditions over Southern Africa. Results are presented to show, first, the spatial and point characteristics of mean non-surface inversions by season and by month, and secondly, the nature of inversion occurrence within six layers of the lower atmosphere.

Journal ArticleDOI
TL;DR: Total control of seizures in a woman with catamenial epilepsy was achieved using norethisterone (the “mini‐pill”).
Abstract: ummary Total control of seizures in a woman with catamenial epilepsy was achieved using norethisterone (the “mini-pill”). RESUME Chez une femme ayant une epilepsie catameniale, on a obtenu un controle complet des crises en utilisant le norethisterone (la mini-pillule). RESUMEN Se ha conseguido un control total de los ataques en una mujer con epilepsia catamenial mediante la utiliza-ci6n de noretisterona (la mini-pildora). ZUSAMMENFASSUNG Vollige Anfallskontrolle bei einer Frau mit “Monats-epilepsie” wurd mit Norethisteron, der “Mini-Pille” erreicht.

Journal ArticleDOI
TL;DR: In this article, the authors made intensive observations on 27 boreholes and several shallow wells, situated in the sand-covered area of Orapa, in the northern Kalahari.

Journal ArticleDOI
TL;DR: A microbiological investigation of Black infants suffering from severe acute summer gastroenteritis revealed enteropathogenic agents in 30 out of 37 patients (81%) and no significant difference in clinical presentation was noted between the various aetiological agents.
Abstract: A microbiological investigation of Black infants suffering from severe acute summer gastroenteritis revealed enteropathogenic agents in 30 out of 37 patients (81%). Enterotoxigenic bacteria were isolated from 15 patients (41%). A total of 16 enterotoxigenic strains were isolated, comprising 9 enterotoxigenic Escherichia coli strains secreting labile and stable toxin on their own and in combination, and labile-toxin secreting strains of Klebsiella pneumoniae (4), Enterobacter cloacae (2) and Proteus vulgaris (1). In the case of the latter three species, however, 6 out of the 7 strains were isolated from patients who were excreting other enteric pathogens, whereas only 2 out of 9 enterotoxigenic E. coli patients had concomitant infections with other pathogens. No invasive bacteria were isolated except for 2 shigella strains. Salmonella and shigella strains were found in four patients. No correlation was found between the enteropathogenicity of E. coli and its serotype. Rotavirus was observed by negative staining electron microscopy in only two patients (6%) but using a reverse complement fixation test rotavirus antigen was detected in the stool of 17 out of 35 patients (49%). The low EM detection rate may well be due to the patients being admitted for treatment late in the course of their illness when the degree of viral shedding has decreased below EM detectability. No significant difference in clinical presentation was noted between the various aetiological agents. Only one patient was being solely breast-fed compared to 16% of control non-diarrhoeic infants. Evidence of malnutrition was noted in over half of our patients.

Journal ArticleDOI
TL;DR: Subtidal and intertidal clastic and carbonate deposits are recognized from the upper part of the 2200 m.y. Pretoria Group in the eastern Transvaal, South Africa.

Journal ArticleDOI
TL;DR: Two methods are described for percutaneous catheterization of the internal jugular vein in children and the technique can be used even in premature babies.

Journal ArticleDOI
TL;DR: A 48 year old premenopausal woman presented with galactorrhea and amenorrhea associated with chest wall burns and intercostal nerve block and bromocryptine treatment reduced prolactin levels to normal, but did not noticably reduce milk secretion.
Abstract: A 48 year old premenopausal woman presented with galactorrhea and amenorrhea associated with chest wall burns. Basal serum prolactin levels were raised, and were further elevated by the administration of L-dopa, chlorpromazine and TRH. Intercostal nerve block and bromocryptine treatment reduced prolactin levels to normal, but did not noticably reduce milk secretion.

Journal ArticleDOI
TL;DR: Endocrine studies were performed on twelve patients with proven idiopathic haemochromatosis, and no patient showed hypothyroidism of hypothalamic‐pituitary origin, while the cortisol response to hypoglycaemia was normal in all six patients studied.
Abstract: Endocrine studies were performed on twelve patients with proven idiopathic haemochromatosis. Basal gonadotrophin levels and/or their responses to LH releasing hormone (LHRH) were low in nine patients, all of whom showed low plasma testosterone levels and clinical evidence of hypogonadism. Those patients with normal gonadotrophin responses had higher testosterone values, suggesting that the poor testosterone secretion was primarily due to inadequate trophic stimulation. No patient showed hypothyroidism of hypothalamic-pituitary origin, while the cortisol response to hypoglycaemia was normal in all six patients studied. GH responses were more variable and difficult to interpret, since the number of the patients studied was small and the degree of hypoglycaemia after insulin was unpredictable.

Journal ArticleDOI
TL;DR: In this paper, the Agulhas Basin is interpreted to be of oceanic origin and the magnetic results support the interpretation of a volcanic constitution, which is not clear, but several possible models are suggested.
Abstract: Refraction data from the Agulhas Basin, south of southern Africa, show a crustal structure compatible with deep-water marine stations. Moho is about 10 km deep, and the crust is believed to be of oceanic origin. On the Agulhas Plateau, a basement layer having a seismic velocity of 4.84 km/s overlies the main crustal layer with velocity 6.72 km/s. This structure is not continental but resembles that of certain volcanic features in the Indian and Pacific Oceans, such as the Chagos-Laccadive and Hawaiian Ridges. The Agulhas Plateau is interpreted to be of oceanic origin. The plateau can be divided into two physiographic provinces. The southern province is characterized by a smooth basement overlain by relatively undisturbed sediment 0.5 to 1.0 km thick. In the northern province the basement topography is rough. The origin of the relief is not clear, but several possible models are suggested. The influence of bottom currents is marked in this region, and the sediments are more disturbed. Large magnetic anomalies are found over the plateau, many of which are generated by basement topography. Remanent reversal stripes cannot be identified with certainty. Magnetic models that incorporate the basement relief suggest that the basement material is basalt. The magnetic results support the refraction interpretation of a volcanic constitution. The Agulhas Plateau was apparently formed during or after the separation of the Falkland Plateau from southern Africa.