Showing papers by "University of the Witwatersrand published in 1988"
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08 Dec 1988TL;DR: The megaherbivore syndrome (MHS) was first identified in the late Pleistocene epoch as mentioned in this paper and has been identified as a major cause of extinction in humans.
Abstract: Prologue 1. Morphology, evolutionary history and recent distribution 2. Food and other habitat resources 3. Space-time patterns of habitat use 4. Body size and nutritional physiology 5. Body size and feeding ecology 6. Social organisation and behaviour 7. Life history 8. Body size and sociobiology 9. Body size and reproductive patterns 10. Demography 11. Community interactions 12. Body size and population regulation 13. Body size and ecosystem processes 14. Late Pleistocene extinctions 15. Conservation Epilogue: the megaherbivore syndrome Appendixes References Index.
929 citations
TL;DR: The objectives of correct histological diagnosis, subclassification and appropriate therapy are best achieved by enucleation biopsy, and there is little evidence to support origin from pre-existing odontogenic cysts.
Abstract: A clinicopathological study of 57 unicystic ameloblastomas has been undertaken, which represents 15% of all cases of ameloblastoma accessioned in our department over a 30-yr period. Of the cases where gender was recorded: 30 were male and 23 female. The majority of patients were black (51 cases) and most occurred in the mandible (52). This distribution conforms to that of solid and multicystic ameloblastomas. The mean age at diagnosis was 23.8 years (S.D. 14.9) which is significantly younger than for the conventional counterpart (p less than 0.1%). The lesions were classified histologically into 3 groups: Group 1 (42%) cyst lined by a variable often non-descript epithelium; Group 2 (9%) cyst showing intraluminal plexiform proliferation of epithelium; Group 3 (49%) cyst with invasion of epithelium into the cyst wall in either follicular or plexiform patterns. While Group 1 and 2 lesions may be treated by enucleation, Group 3 lesions should be treated aggressively as for conventional ameloblastomas. The objectives of correct histological diagnosis, subclassification and appropriate therapy are best achieved by enucleation biopsy. There is little evidence to support origin from pre-existing odontogenic cysts.
308 citations
TL;DR: In this article, zero-lag correlations between the Tahiti-Darwin Southern Oscillation Index and monthly and 3-month seasonal rainfall over South Africa suggest that the rainfall-SOV association is best defined in the late summer season January-March and in a north-west to south-east aligned zone across the central summer rainfall region of South Africa.
Abstract: Significant differences in rainfall over central South Africa are known to occur between opposite extremes in the phase of the Southern Oscillation, but details of both temporal and spatial aspects of the modulation of South African rainfall with the phase changes of the Oscillation remain to be described. Zero-lag correlations between the Tahiti—Darwin Southern Oscillation Index and monthly and 3-month seasonal rainfall over South Africa suggest that the rainfall—Southern Oscillation Index association is best defined in the late summer season January—March and in a north-west to south-east aligned zone across the central summer rainfall region of South Africa. Rainfall in this zone is directly related to the Southern Oscillation Index, increasing during high phase summers. An apparent semi-annual cycle in the rainfall—Southern Oscillation Index correlations over central South Africa is in phase with the November and February turning points of a semi-annual cycle in atmospheric circulation parameters over southern Africa. A plausible circulation mechanism is suggested to account for some of the spatial and temporal characteristics of the association between the Southern Oscillation and South African rainfall.
253 citations
TL;DR: The role of the lone pair of electrons on Pb(II) in its coordination geometry and complex stability is examined in this paper, where it is found that when three or four nitrogens are present, there is a sudden marked increase in the rate of change of complex stability per nitrogen donor added.
220 citations
TL;DR: It is concluded that the response to stress has two phases, a hypothalamic-adrenal cortex phase which is associated with perceived environmental stress such as noise, and a sympathetic- adrenal-medulla phase which was associated with neurogenic stresssuch as transport or specifically the massive sympathetic discharge caused by stunning.
Abstract: Blood samples were collected from unstressed cattle and from cattle undergoing handling stress, transport stress and slaughter. The blood was analysed for ACTH, cortisol, thyroxine stimulating hormone, tri-iodothyronine (T3) and catecholamine concentrations, and for haematocrit, total plasma protein, plasma lipid, lactate and glucose concentrations. Compared to control values handling significantly increased T3, cortisol, lipid and lactate concentrations. Compared to handling, transport stress was associated with increased catecholamines and lactate concentrations, a decreased cortisol concentration and similar concentrations of T3, lipid and glucose. Compared to transport, slaughter resulted in high catecholamines, lactate and glucose, and low T3, cortisol and lipid levels. It is concluded that the response to stress has two phases, a hypothalamic-adrenal cortex phase which is associated with perceived environmental stress such as noise, and a sympathetic-adrenal-medulla phase which is associated with neurogenic stress such as transport or specifically the massive sympathetic discharge caused by stunning. Combinations of stresses produce a mixed response.
200 citations
TL;DR: In this paper, the conductivity of four graphite powders was measured as a function of the volume fraction of graphite (or air) along (axial) and across (transverse) the direction of compression.
Abstract: The conductivity of four graphite powders was measured as a function of the volume fraction of graphite (or air) along (axial) and across (transverse) the direction of compression. The conductivity varies by between two and four orders of magnitude during these measurements. The results are shown to fit an equation which expresses the conductivity of the mixture as a function of the conductivity of the graphite and two morphology parameters. One parameters is the critical volume fraction, at which the graphite-air mixture would become insulating (percolation threshold) and the other an exponent is a combination of the effective demagnetisation coefficients of the grains and the critical volume fraction. Electron micrographs of the powder grains are shown and volume orientation percentage measurements of the graphite using X-rays were made in order to try to understand the results better.
157 citations
TL;DR: A comparative study of the activity of carbon supported metal chlorides for the hydrochlorination of acetylene is described in this paper, where the results confirm that the standard electrode potential of the metal is a useful correlation parameter and confirm a previous prediction that catalysts based on gold are particularly active.
150 citations
TL;DR: In this article, different ratios of boron to carbon ions were implanted into diamond maintained at liquid-nitrogen temperature, and the diamonds were heated to 500 \ifmmode^\circ\else\textdegree\fi{}C by dropping them onto a platform situated in a vertical tube furnace, and then annealed for 1 h.
Abstract: Different ratios of boron to carbon ions were implanted into diamond maintained at liquid-nitrogen temperature. After implantation, the diamonds were heated to 500 \ifmmode^\circ\else\textdegree\fi{}C by dropping them onto a platform situated in a vertical tube furnace, and then annealed for 1 h. This was followed by a further anneal at 1200 \ifmmode^\circ\else\textdegree\fi{}C in an argon atmosphere. It was found that under suitable conditions optical and electrical properties could be obtained which correlated with those found in natural semiconducting diamond. Thermally activated electrical conduction could, for instance, be established at an activation energy of \ensuremath{\sim}0.37 eV, which corresponds to the value measured for substitutional boron acceptors in diamond. Owing to the annealing cycle used, a relatively large amount of products resulting from radiation damage remained, which, in the carbon-ion-implanted diamond, manifested itself by increased optical absorption at short wavelengths. The results indicate that the product responsible for this absorption may be acting as a donor center situated at about 4 eV below the conduction band. Thermal electromotive-force measurements correlate with the movement of holes in the valence band.
147 citations
TL;DR: In this paper, the authors present the development of a marketing philosophy, discusses the influence of consumerism on the marketing concept and deals with ethics and social responsibility in marketing, arguing that organisations who adopt the societal marketing concept will be the ones most likely to make long-run profits as well as be beneficial to society as a whole.
Abstract: This article reviews the history of marketing thought in relation to social responsibility and business ethics. The main objective of the article is to show that business can be profitable and socially responsible at the same time by practising the societal marketing concept. More specifically, it presents the development of a marketing philosophy, discusses the influence of consumerism on the marketing concept and deals with ethics and social responsibility in marketing. It is argued that organisations who adopt the societal marketing concept will be the ones most likely to make long-run profits as well as be beneficial to society as a whole.
139 citations
TL;DR: In an analysis of 4766 consecutive strains of Streptococcus pneumoniae isolated from cultures of blood from 1979 to 1986 and of 1157 isolates from cerebrospinal fluid (CSF), resistance was found in 380 (8%) of blood and 107 (9.2%) of CSF isolates to one or more of the following antibiotics.
Abstract: In an analysis of 4766 consecutive strains of Streptococcus pneumoniae isolated from cultures of blood from 1979 to 1986 and of 1157 isolates from cerebrospinal fluid (CSF), resistance was found in 380 (8%) of blood and 107 (9.2%) of CSF isolates to one or more of the following antibiotics: penicillin, tetracycline, erythromycin, clindamycin, rifampin, and chloramphenicol. Resistance increased from 3.8% to 14.1% among isolates from blood and from 6.8% to 14.1% among CSF isolates during this period. Comparing 1979-1982 with 1983-1986, we found that significant increases (P less than .01) have occurred in penicillin resistance alone, rifampin resistance alone, and in strains showing multiple resistance. Resistance was found in 15 different serogroups and/or serotypes, although 92.2% of resistant strains belonged to serogroups 6 or 19 or to serotype 14. Of the serogrouped or serotyped strains, 97.4% are represented in the 23-valent vaccine by a vaccine or vaccine-related strain.
133 citations
TL;DR: In this article, the chelate, macrocyclic, and cryptate effects are analyzed and it is concluded that for all three effects considerable stabilization is derived from the greater basicity induced in donor atoms as ethylene bridges are added.
Abstract: The chelate, macrocyclic, and cryptate effects are analyzed. It is concluded that for all three effects considerable stabilization is derived from the greater basicity induced in donor atoms as ethylene bridges are added. Further considerations of importance in these effects are (1) desolvation effects, where steric constraints to solvation of the donor atoms in the free ligand lead to increased complex stability, (2) enforced dipole-dipole repulsion in the ligand, which is relieved on complex formation, and (3) structural preorganization of the ligand such that the donor atoms in the free ligand are already correctly oriented for complex formation. Only for the chelate effect is entropy of paramount importance, where it is derived from a cratic effect. It is emphasized that the level of preorganization of macrocycles, and to a lesser extent cryptands, is much lower than commonly realized. Newly emerging types of more highly preorganized ligands are discussed.
TL;DR: The radiologic features of 16 cases of central giant cell granuloma of the jaws were studied and one of the most consistent features found was splaying of the roots of teeth adjacent to the lesion.
TL;DR: In this article, the authors presented ten plate tectonic reconstructions of the Southwest Indian Ridge that were produced using a new compilation of magnetic, bathymetric and satellite altimetry data, in combination with interactive computer graphics.
TL;DR: Gustav Preller (1875-1943) is the man largely responsible for shaping many of the key myths of Afrikaner nationalism as mentioned in this paper, one of which is the concept of the Great Trek, an interpretation of the nineteenth-century movement of Boers into the interior.
Abstract: Gustav Preller (1875–1943), a prolific and popular South African historian, is the man largely responsible for shaping many of the key myths of Afrikaner nationalism. One of these is the concept of the Great Trek, an interpretation of the nineteenth-century movement of Boers into the interior. It is Preller's written and visual version of this social movement that has been the dominant one for the last seven decades. Preller worked with a variety of media including books, newspapers, magazines, drama and film, and always produced works that sold in significant numbers. Yet despite his obvious impact and importance, Preller has been the subject of little research. This article attempts to assess Preller's work in relation to questions concerning the cultural fabrication of nationalisms. It asks how Preller did his popularizing work: what techniques, conventions, narrative formulas and social languages did he deploy in his work and whence did he derive these cultural resources? For Preller, one of the most crucial themes in his work had to do with how people recalled the past and more importantly how one could get them to ‘enact’ this memory in their own lives. Much of his work can be read as a search to find strategies of storing the past in forms which would make popular sense. He relied heavily on oral history and he also familiarized himself with popular forms of both oral and written storytelling which in turn inform his work. In 1916 he became involved in filming De Voortrekkers and these visual skills became a key ingredient in all of his ventures. His interest in the visual also informed his frequent use of the physical objects of the past as vehicles for popularizing his views. Another tactic that Preller followed was to explore and ‘colonize’ the institutions of popular leisure which he then remoulded in his nationalist enterprises. The article concludes with a detailed consideration of one of Preller's historical short stories.
TL;DR: It is concluded that continued evaluation of this technique is justified and papaverine was not associated with increased risk and may be superior to other conventionally used modalities.
TL;DR: It is suggested that decreased or defective core antigen production can lead to reduced viremia associated with blocked virus assembly/secretion and accumulation of unencapsidated HBV DNA replicative intermediates in the liver cell.
TL;DR: Female painted reed frogs, Hyperolius marmoratus, were subjected to two-choide discrimination experiments to determine whether temporal overlap in the presented stimuli affects frequency preferences, showing that females preferred low frequency calls when the stimuli were presented alternately.
TL;DR: Relative growth rate (whole plant) was initially lower for seedlings grown under the lowest light treatments, but with time, higher leaf area ratio offset lower net assimilation rate for the two lowest light treatment, eliminating differences in relative growth rate among treatments.
TL;DR: San rock art comprises depictions which are uniform, resulting from a combination of neurological and cultural factors, as well as idiosyncratic or nonce depictions resulting from idiosyncratic revelations.
Abstract: San ethnography concerning the personal nature of religious beliefs contradicts the view that San rock art, essentially a religious art, is uniform due to social control. There are, however, rare paintings and engravings that show that some idiosyncrasy does exist. Because these idiosyncratic depictions were created under certain social conditions and constraints, they are explicable within the framework of the San cognitive system. They are thought to be expressions of religious beliefs comparable with the ethnographic accounts of individual religious revelations. San rock art comprises depictions which are uniform, resulting from a combination of neurological and cultural factors, as well as idiosyncratic or nonce depictions resulting from idiosyncratic revelations.
TL;DR: The present case is unusual in that the neuropsychological status of the patient is investigated in some detail, and in that it seems to be the first report of inverted vision in a case of frontal lobe disease.
TL;DR: The fossil evidence suggests that Homo habilis and Paranthropus may have attained a similar grade of bipedality at roughly 1.8 m.y. BP, and the base, shaft, and head of SKX 5017 suggest human-like foot posture and a human- like range of extension at the hallucal metatarsophalangeal joint.
Abstract: A new, complete hallucal metatarsal (SKX 5017) was recovered from the “lower bank” of Member 1 at Swartkrans (ca. 1.8 m.y. BP). The new metatarsal is attributed to Paranthropus robustus, the predominant hominid found in Member 1 (>95% of hominid individuals). SKX 5017 is similar to Olduvai Hominid 8-H from bed I, Olduvai (ca. 1.76 m.y. BP), and both resemble humans most closely among extant hominoids. The base, shaft, and head of SKX 5017 suggest human-like foot posture and a human-like range of extension (= dorsiflexion) at the hallucal metatarsophalangeal joint, while at the same time the distal articular surface indicates that a human-like toe-off mechanism was absent in Paranthropus. The fossil evidence suggests that Homo habilis and Paranthropus may have attained a similar grade of bipedality at roughly 1.8 m.y. BP.
TL;DR: Gut content data indicate a variety of foods, with a preponderance in the northern localities of soft fruit such as mango, pawpaw, and coconut pulp; gum was a major carbohydrate source in the southernmost localities.
Abstract: Information concerning habitat, body size, reproductive status, and diet was recorded from 348 greater galagos, captured at six different localities in Tanzania and southern Africa between 1953 and 1955. The localities extended from Pemba Island in the north to Chikwawa, Malawi, in the south and varied broadly in the same order in degree of climatic aridity— from well-watered clove and coconut plantations to seasonally very dry woodland. Animals from the three northern localities fell within the geographic range of Galago garnettii,while the rest were assumed to be G. crassicaudatus.Statistical analysis of body size parameters confirmed this allocation. Data on fetal occurrence, vaginal and labial condition, and lactation indicate a restricted breeding season for both species, with peak proportions in estrus in August in G. garnettiiand in May-July in G. crassicaudatus.Gut content data indicate a variety of foods, with a preponderance in the northern localities of soft fruit such as mango, pawpaw, and coconut pulp; gum was a major carbohydrate source in the southernmost localities. Contrary to expectations, tooth damage, in the form of both loss and breakage, was much more prevalent in G. garnettiithan in G. crassicaudatus.The teeth most commonly lost were the upper incisors— perhaps because of the high acid and sugar content of a frugivorous diet. The high incidence of breakage of the lower incisors and upper canines indicates the inclusion of hard-shelled food sources in the diet of G. garnettii.
TL;DR: It is concluded that whereas the association between hepatocellular carcinoma and hepatitis B infection is almost universal in young blacks, a subgroup of older blacks shows no evidence of ever having been infected with this virus.
TL;DR: A model, based on a fuzzy relation obtained from fuzzy referential sets on the input and output spaces, for predicting the behaviour of nonlinear dynamic systems is presented.
Abstract: We present a model, based on a fuzzy relation obtained from fuzzy referential sets on the input and output spaces, for predicting the behaviour of nonlinear dynamic systems. The model can be made to learn from experience, and the computing requirements are modest, making online application feasible. Some numerical results are compared with those of earlier models.
TL;DR: This report describes, for the first time, an enlarged occipital-marginal sinus system on the endocranial cast of the Taung specimen, which is part of the holotype of A. africanus.
Abstract: According to published accounts, an enlarged occipital-marginal sinus system is absent in Australopithecus africanus, although it occurs in high frequencies in A. robustus, A. Boisei, and Hadar hominids commonly designated A. afarensis. In this report, we describe, for the first time, an enlarged occipital-marginal sinus system on the endocranial cast of the Taung specimen, which is part of the holotype of A. africanus. In addition, well-developed right transverse and sigmoid sinuses are represented on the Taung endocast. The various components of the dual venous sinus system on the Taung endocast are measured, and the system is compared to those of other fossil hominids. The compresence of a lateral sinus system and enlarged occipital and marginal sinuses occurs in two Hadar specimens, 2 specimens of A. robustus crassidens, 1 A. boisei specimen, and several early H. sapiens crania. Hence, the presence of strong transverse sinus impressions in a fragmentary specimen may not be interpreted as an indication that an enlarged occipital-marginal sinus system was not present in the original specimen. Conversely, lack of transverse sinus grooves in a fragmentary specimen does provide indirect evidence than an enlarged occipital-marginal system would probably have been present in the whole specimen, as in 2 specimens of A. boisei. Including Taung, enlarged occipital and marginal sinuses occur in 1 out of 5, or 20%, of A. africanus specimens. This figure compares well with the range of mean frequencies in modern human cranial series (1.5 to 28%), but is much lower than are the frequencies for A. boisei, A. robustus, and the Hadar hominids. Although sample sizes for ancient hominids remain small, it appears that we are dealing with a genetic polymorphism that expresses itself in widely varying frequencies in populations of different hominids.
TL;DR: When analyzed against the background of an essentially noncompliant population group, the Medtronic Hall prosthesis proved to be reliable and remarkably free from structural failure.
TL;DR: A number of relatively undeformed late middle Proterozoic volcano-sedimentary basins are aligned along the western and northern margins of the Kalahari Craton.
TL;DR: The article suggests the need for a life span developmental perspective in LOC research, and studies which explore the influence of life experiences, situational and environmental variables, and their effect on control orientation are also needed.
Abstract: The present study examined Rotter's Internal-External (I-E) locus of control (LOC) concept in relation to life satisfaction and death anxiety in an aged population. Age and sex of the individual were also considered. In the case of life satisfaction, a strong sex and a strong locus of control effect were found. For death anxiety, again a strong sex effect was found, but there was also a significant interaction between locus of control and age. The article suggests the need for a life span developmental perspective in LOC research. Studies which explore the influence of life experiences, situational and environmental variables, and their effect on control orientation are also needed.
TL;DR: In this article, fluid migrations of saline brines are discussed, together with Pb-Pb isotope data that are consistent with collisioninduced (Laurentia-Baltica-Gondwana) tectonic plumbing systems through which ore fluids were driven to distant structural sites.
Abstract: Pb-Zn ore deposits within the northern Caledonides formed in compressional environments associated with major thrust sheets that were emplaced over foreland sediments during the final closure of the proto-Atlantic. Fluid migrations of saline brines are discussed, together with Pb-Pb isotope data that are consistent with collisioninduced (Laurentia-Baltica-Gondwana) tectonic plumbing systems through which ore fluids were driven to distant structural sites. Pb- isotope data from widely separated ore deposits across the orogen fall on a Pb-Pb linear array equivalent to a 2.05 Ga isochron; μvalues ( 238 U/ 204 Pb) increase from the central parts of the orogen toward its forelands. The array is interpreted as a Pb mixing line for averaged basement (3.8-0.6 Ga) and juvenile Paleozoic mantle Pb within the Caledonian orogen. Continued convergence and thrusting during the closing of the proto-Atlantic activated fluids within the sedimentary column and forced the escape and focusing of ore-bearing brines along horizontal and vertical decollements. Toward the forelands, the fluids interacted increasingly with older basement or sediments derived thereof. The process may have applications in deciphering collisional events and tectonic-fluid transport directions within older orogens.