Showing papers by "University of the Witwatersrand published in 1986"

Effects of plant spinescence on large mammalian herbivores

Abstract: Plant thorns and spines had these effects on the feeding behaviour of the three species of browsing ungulate that we studied, kudu, impala and domestic goats: (i) bite sizes were restricted, in most cases to single leaves or leaf clusters; (ii) hooked thorns retarded biting rates; (iii) the acceptability of those plant species offering small leaf size in conjunction with prickles was lower, at least for the kudus, than those of other palatable plant species; (iv) the inhibitory effect of prickles on feeding was much less for the smaller impalas and goats than for the larger kudus; (v) from certain hook-thorned species the kudus bit off shoot ends despite their prickles; (vi) for certain straight-thorned species the kudus compensated partially for the slow eating rates obtained by extending their feeding durations per encounter. Most spinescent species were similar in their acceptability to the ungulates to unarmed palatable species, despite higher crude protein contents in their foliage than the latter. Such structural features furthermore reduce the tissue losses incurred by plants per encounter by a large ungulate herbivore, by restricting the eating rates that the animals obtain. In this way prickles function to restrict foliage losses to large herbivores below the levels that might otherwise occur.

Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons.

Abstract: There is a high incidence of paraplegia associated with thoracic aortic cross-clamping, even when cardiopulmonary bypass or shunts are used. In 56 adult baboons, spinal cord blood flow (SCBF), vascular anatomy, and paraplegia rates were evaluated. Tissue blood flow was measured by radioactive microspheres. Various procedures were used to increase SCBF and to prevent ischemia-reperfusion injury. It was found that the rate of paraplegia was inversely correlated with neural tissue ischemia (SCBF) and directly correlated with reperfusion hyperemia. Two methods completely prevented paraplegia. These two methods were a thoracic shunt with occlusion of the infrarenal aorta or cerebrospinal fluid drainage plus intrathecal papaverine injection, both of which were associated with an increased SCBF. Furthermore, papaverine dilated the anterior spinal artery (ASA) (p = 0.007) and increased the blood flow through the lower ASA. Whereas procedures utilizing a calcium channel blocker (flunarizine), allopurinol, superoxide dismutase (SOD), laminectomy alone, and a thoracoabdominal shunt not perfusing the arteria radicularis magna (ARM) all failed to prevent paraplegia, allopurinol (p = 0.026) and SOD (p = 0.004) did prevent gastric stress lesions, indicating that their failure to prevent paraplegia was not due to a lack of activity. Of great clinical interest is that, if a shunt is used and the ARM is perfused, infrarenal aortic cross-clamping increases SCBF, thus preventing paraplegia. Intrathecal application of papaverine proved to be even more effective in increasing SCBF and also completely prevented paraplegia. As this is a safer procedure than the insertion of shunts, this is the method of choice for the prevention of paraplegia associated with thoracic aortic cross-clamping. The preliminary trial using intrathecal papaverine in human beings has thus far shown no adverse side effects from the drug, and no paraplegia has occurred.

Criteria for comparison of single event models

Abstract: Methods of assessing the goodness-of-fit of hydrological simulation models are discussed. The methods generally compare the goodness-of-fit of a simulated hydrograph with an observed one and invariably have a bias towards one or another aspect of the hydrograph. It appears that no single parameter is sufficient to assess adequately the overall measure of fit between a computed and an observed hydrograph, particularly in view of the many objectives behind hydrological modelling. Previous research has concentrated on assessing the goodness-of-fit of long duration hydrographs resulting from continuous simulation. This paper discusses a number of criteria for hydrograph comparison in single event modelling studies and applies them to a specific stormwater modelling exercise. It is shown that particular criteria highlight particular aspects.

Female age: Male preference and reproductive success in primates

Abstract: A survey of the literature on male sexual preferences according to the age of the female partner supported the hypothesis that adult males should prefer older females of higher parity. Reproductive success was also surveyed by age and parity, and younger females of lower parity were universally found to have lower success than older females of higher parity. This appears to be true for either age or parity independently, as well as in combination. These findings are discussed and applied to human societies, where similar trends would be expected.

The non-immune inflammatory response : serial changes in plasma iron, iron-binding capacity, lactoferrin, ferritin and C-reactive protein

Abstract: The interrelationships between various components of the non-immune inflammatory response (white cell count, plasma lactoferrin, C-reactive protein, ferritin, iron and iron-binding capacity), were studied serially in a variety of inflammatory conditions including acute lobar pneumonia, active pulmonary tuberculosis, rheumatoid arthritis on gold therapy and sepsis in the face of marrow hypoplasia induced by chemotherapy. Lactoferrin concentrations paralleled the white count in all groups. They were highest in pneumonia and tuberculosis, mildly elevated in rheumatoid arthritis and markedly decreased in neutropenic sepsis. Very high initial lactoferrin concentrations were associated with a poor prognosis in acute pneumonia. C-reactive protein and ferritin concentrations remained elevated through the period of study in acute pneumonia and neutropenic sepsis, while they gradually normalised over weeks in subjects with tuberculosis or rheumatoid arthritis on therapy. In pneumonia and tuberculosis moderate hypoferraemia and a reduced iron-binding capacity were evident. In contrast, a raised percentage saturation was present in neutropenic sepsis, probably related to erythroid marrow suppression. Comparisons between ferritin, lactoferrin and C-reactive protein in the various groups supported the concept that ferritin behaves in part as an acute phase reactant and that hypoferraemia in inflammation is due to deviation of iron into ferritin stores. The suggestion that lactoferrin is responsible for the hypoferraemia and hyperferritinaemia was not supported by the present data. Iron deficiency appeared to limit the hyperferritinaemic response in rheumatoid arthritis, while erythropoietic inhibition by chemotherapy dampened the hypoferraemic response in neutropenic sepsis.

Effect of instruction using microcomputer simulations and conceptual change strategies on science learning

Abstract: This article describes an investigation into the effects of instruction using microcomputer simulations and conceptual change strategies. The microcomputer program was designed in accord with a model of conceptual change to diagnose and remediate an alternative conception of velocity. Results show that, first, the microcomputer simulations are credible representations of reality, and second, that the remedial part of the program produced significant conceptual change in students holding the alternative conception.

Conformal Killing vectors in Robertson-Walker spacetimes

Abstract: It is well known that Robertson-Walker spacetimes admit a conformal Killing vector normal to the spacelike homogeneous hypersurfaces. Because these spacetimes are conformally flat, there are a further eight conformal Killing vectors, which are neither normal nor tangent to the homogeneous hypersurfaces. The authors find these further conformal Killing vectors and the Lie algebra of the full G15 of conformal motions. Conditions on the metric scale factor are determined which reduce some of the conformal Killing vectors to homothetic Killing vectors or Killing vectors, allowing the authors to regain in a unified way the known special geometries. The non-normal conformal Killing vectors provide a counter-example to show that conformal motions do not, in general, map a fluid flow conformally. They also use these non-normal vectors to find the general solution of the null geodesic equation and photon Liouville equation.

Kinematic and dynamic properties of conformal Killing vectors in anisotropic fluids

Abstract: An example from a perfect fluid FRW space‐time is presented to show that a conformal Killing vector (CKV) need not map fluid flow lines into fluid flow lines. Kinematic properties of the Lie derivative along a CKV of timelike and spacelike unit vectors are derived and applied to the fluid unit four‐velocity vector. Dynamic properties of special conformal Killing vectors (SCKV) in a fluid with anisotropic pressure and vanishing energy flux are obtained using Einstein’s field equations. It is shown that a SCKV maps both fluid flow lines and integral curves of na into themselves, where na is the unit spacelike vector of anisotropy. The relation between the anisotropic pressure components and the energy density is considered. By means of an example from a radiationlike viscous fluid FRW space‐time it is shown that the dynamic results depend crucially on the vanishing of the energy flux vector. The extension of the dynamic results to a fluid with arbitrary stress tensor and zero energy flux vector is examined.

Age estimation of the White rhinoceros (Ceratotherium simum)

Abstract: Age estimation criteria for the southern White rhinoceros (Ceratotherium simum simum) are presented both for free-ranging live animals and for cranial material. These are based on: (i) size appearance and horn development of live animals; (ii) stages of tooth eruption; (iii) tooth wear classes; (iv) attrition in height of the first molar tooth; (v) counts of cementum lines visible in tooth sections. Selected measurements are presented for live animals, skulls and horns. For live animals, eight size classes are distinguished, seven of these covering immature animals up to ten years of age. Sixteen tooth wear classes are established, based on eruption and surface wear of maxillary dentition. Chronological ages were assigned from individually known animals followed in the field, and from skulls from animals for which exact records of age were available, or which could be assigned to an age category from appearance at death. Cementum line counts corresponded approximately with age in years, despite difficulties in interpreting lines. Some variability was observed, possibly related to nutritional conditions. The maximum cementum line count obtained indicates a longevity of at least 40 years. Full body weight and socio-sexual maturity are attained by males between 10 and 15 years of age, while females first give birth between six and eight years of age. Sequences and times of tooth eruption are similar to those reported for the Black rhinoceros (Diceros bicornis). Comparative cranial and body measurements are presented for the northern subspecies (Ceratotherium simum cottoni).

Predation and primate evolution

Abstract: This paper presents the results of a general review of predation on nonhuman primates as a selective force in primate evolution. Testable hypotheses derived from the literature on predation on primates, concerning sexual dimorphism, male defense, group size, solitaries, transfer, subgrouping, and sex ratio, were applied to the available data on populations with varying predation rates in search of significant correlations. All seven hypotheses were supported, indicating that predation is and has been an important determinant of primate evolutionary history. Suggestions for accumulating a larger and more accurate body of information on predation rates on primates are offered.

Employed mothers: Interrole conflict, spouse support and marital functioning

Abstract: SUMMARY Increased participation by mothers in the labour force may exert a negative effect on working mothers themselves (e.g. interrole conflict) and influence the marital relationship negatively. Recent research suggests that not all individuals experiencing psychological distress suffer psychological strain (e.g. marital discord). Rather, variables such as social support moderate negative effects of psychological stressors. To test this, sixty-four employed mothers (M age = 36 years) completed interrole conflict and spouse support scales. Marital satisfaction, verbal and nonverbal communication were the criteria operationalized to assess marital functioning. Using moderated multiple regression analyses, interrole conflict and spouse support predicted marital satisfaction and verbal communication significantly. In addition, spouse support may moderate negative effects of interrole conflict on marital satisfaction and verbal communication. With regard to nonverbal communication, spouse support was both a significant main effect and possibly a moderator of interrole conflict. The role of spouse support, conceptual and treatment implications, and future research priorities are identified.

Seasonal variation in the diet of South African Galagos

Abstract: The feeding behavior and diet of two species of bushbaby, Galago senegalensisand Galago crassicaudatus,in South Africa were examined in relation to seasonal changes in climate. The populations studied were allopatric, but both fed predominantly on Acaciagum and invertebrates. Data on their diet were collected by direct observation of a radiocollared female of each species and by analysis of fecal samples. Differences in diet were found between the species within seasons and within species between the seasons. Both spent more time gum-feeding in winter than in summer. Prey size and type differed between the species in summer but converged in winter. The quantity of insects taken was fairly similar between seasons for G. senegalensisbut dropped considerably for G. crassicaudatusin winter. These observations are interpreted in terms of interspecific differences in feeding strategies, which are considered to be a function of the difference in body size of the two galago species.

Comparison of techniques for demonstrating antibodies to Rift Valley fever virus

Abstract: Nine serological techniques were compared by monitoring the response to infection with Rift Valley fever (RVF) virus in three sheep. Antibodies were monitored daily for the first 14 days after infection, then weekly and later fortnightly up to week 24. The earliest antibody response was detected in one sheep on day 3 by a plaque reduction neutralization test, and by day 6 antibodies were demonstrable in all three sheep by haemagglutination-inhibition, reversed passive haemagglutination-inhibition, immunodiffusion, indirect immunofluorescence (IF), enzyme-linked immunosorbent assay and neutralization of cytopathic effect in cell cultures. Antibodies were demonstrable by complement fixation on day 8 at the earliest. IF and the two neutralization techniques produced the highest titres, but all tests could be used satisfactorily for the serological diagnosis of RVF. Inactivated antigen could be used for all except the neutralization tests. A radioimmunoassay technique using 125I-labelled staphylococcal protein A detected antibodies on day 8 at the earliest and produced lower mean titres than some of the other techniques. This was probably because sheep immunoglobulins bind protein A poorly.

Information disclosure in annual reports in South Africa

Abstract: This study examines the information requirements of South African investment analysts and compares them to their United Kingdom counterparts. A disclosure index for measuring the extent of voluntary information disclosure in firm annual reports is developed. The items making up the index are weighted by South African analysts. The results are compared with those of a similar study in the UK. A low level of correlation between the two sets of results is found, indicating that analysts in the two countries appear to have differing information needs. The index is used to measure the extent of actual information disclosure in a sample of listed South African firms. Low levels of disclosure are found, in common with studies in other countries. Finally the perceptions of financial directors of the relative importance of the items making up the index is surveyed. Though not high, the correlation found between the rankings of the index items by the financial directors and actual firm practice is substantially better than the correlation of analyst rankings and firm practice.

On psychoanalysis and neuroscience: Freud's attitude to the localizationist tradition.

Abstract: This study examines the relationship between psychoanalysis and neuroscience. It argues that the Project, the traditional starting-point for such an examination, provides few substantial links between Freud's neurological and psychoanalytic careers. The neurological model that the Project endorsed was not derived from Freud's formal neurological education, as has so often been assumed. It was based, instead, on the Jacksonian model that he developed in 'On aphasia' in 1891. 'On aphasia' appears to be the real 'missing link' between Freud's neurological and psychological years. The fundamental principles that it endorsed provided the framework within which psychoanalysis developed. After Freud's death, Luria developed the science of dynamic neuropsychology, which is based on the same fundamental neurological assumptions as 'On aphasia'. Dynamic neuropsychology approaches brain functioning in a way that would have been entirely acceptable to Freud. Considering the deep-rooted compatibility between Luria's neuropsychology and Freud's psychoanalysis, it would be beneficial for both sciences if they were to collaborate on issues of common interest. This makes Freud's lifelong ambition that psychoanalysis be rejoined with neuroscience a very real possibility.

On the dimensions of ordered sets of bounded degree

Abstract: Let P be a partially ordered set. Define k = k (P) = max p∈ |{x ∈ P : p < x or p = x}|, i.e., every element is comparable with at most k others. Here it is proven that there exists a constant c (c < 50) such that dim P < ck(log k)2. This improves an earlier result of Rodl and Trotter (dim P ≤2 k 2+2). Our proof is nonconstructive, depending in part on Lovasz' local lemma.

Florisbad—New investigations at a middle stone age Hominid Site in South Africa

Abstract: First results of renewed excavations at the Middle Stone Age spring site of Florisbad are reported. Seven meters of deposits dating possibly from the later mid-Pleistocene to the mid-Holocene contain several cultural phases and record alternating periods of increased spring flow versus more stabilized conditions. The archaic Homo sapiens cranium discovered in 1932 and the Florisian Land Mammal Age fauna retrieved from the springs are argued to derive from the earliest deposits, estimated to be ca. 100,000–200,000 years old. In an Upper Pleistocene layer beyond the range of Carbon-14 dating, a Middle Stone Age occupation floor has been excavated. This we interpret as a multiple-occupation kill, butchery, or scavenging site. The presence of a hearth, of chipping debris under 10 mm in size, and the limited displacement of artifacts which have been refitted as conjoining pieces demonstrate a minimally disturbed, primary context site.

Sindbis and West Nile virus infections in the Witwatersrand-Pretoria region

Abstract: From mid-December 1983 until mid-April 1984, there was an epidemic of Sindbis (SIN) virus infection in the Witwatersrand-Pretoria region in which hundreds of human cases were diagnosed clinically. Twenty-eight of these diagnoses were confirmed in the laboratory by seroconversion as being infections with SIN virus, and 5 cases of infection with West Nile (WN) virus were also found. Attempts to isolate virus from 66 patients, mainly from serum specimens, were unsuccessful. Infection rates for the mosquito vector Culex univittatus, collected at localities on the Witwatersrand in February and March, were mostly higher for both SIN and WN viruses than in previous years. The highest rates determined were 5.4 (SIN) and 9.6 (WN) per 1 000 mosquitoes. It is concluded that an epizootic of both viruses occurred which was manifested by a high level of viral activity in the feral Cx. univittatus-bird transmission cycle. Cx. univittatus efficiently transferred infection of SIN virus from this cycle to man to cause the epidemic of infection with that virus but it is unclear why there were apparently only a few cases of WN virus infection.

Images of war: A problem in San rock art research

Abstract: Paintings of conflict are not uncommon in the rock art of southern Africa and are distributed over a wide area. A variety of weapons and forms of conflict are portrayed. These paintings can be considered from two viewpoints: either they are realistic depictions of actual events or else they are essentially hallucinatory, portraying the non‐real world of trance experience. It is argued that, although the selected paintings are highly detailed, they contain postures and hallucinatory features which indicate that they are intimately associated with medicine men and trance.