A comparison of four microcomputer operating systems
- Authors: Wells, George C
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430422 , vital:72690 , https://doi.org/10.1007/BF01088835
- Description: This article describes a comparative study of four operating systems for IBM-PC compatible microcomputers. The assessment concentrated on the suitability of the operating systems for use in real-time applications, and on their use as development environments for real-time systems. The study evaluated the predictability and the performance of the operating systems in several areas critical in real-time systems by using comparative benchmarks. In addition, a small-scale simulation of a process control system was developed for each of the systems. The operating systems that were studied were UNIX, OS/2, QNX and FlexOS. These operating systems represent a broad spectrum of systems from general purpose operating systems to small, specialized real-time operating systems. The details of the evaluation process are given and a summary of the results is presented.
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A critique of the proposed council for the environment national core syllabus for environmental education in South Africa
- Authors: Taylor, Jim , O'Donoghue, Rob B , Clacherty, Allistair
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450119 , vital:74884
- Description: The Department of Environment Affairs, in cooperation with EEASA, undertook a broad consultative process, a central feature of which was the recent Dikhololo Workshop (see Clacherty in this issue). The process led to the Environmental Education Policy Initiative (EEPI), the purpose of which is to foster broad-based processes to promote policy change with respect to environmental education in formal education. The EEPI is not a unilateral initiative; it seeks to work within existing education policy development and change processes.
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An annotated bibliography of the Cape honeybee, Apis mellilera capensis Eschscholtz (Hymenoptera: Apidae)
- Authors: Hepburn, H Randall , Guye, Sally G
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451818 , vital:75079 , https://hdl.handle.net/10520/AJA10213589_64
- Description: An annotated bibliography of all known publications on the biology of the Cape honeybee, Apis mellifera capensis Eschscholtz, is presented. The record covers the period 1778 to 1993 and includes 313 entries. One half of these publications have appeared during the last decade.
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Co-occurrence of mated workers and a mated queen in a colony of Platythyrea arnoldi (Hymenoptera Formicidae).
- Authors: Villet, Martin H
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447377 , vital:74619 , https://hdl.handle.net/10520/AJA00445096_510
- Description: A colony of Platythyrea arnold; was found to contain a functional queen and laying workers, both virgin and mated. This form of social organization has never been reported in ants before.
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Ecological correlates of relative brain size in some South African rodents
- Authors: Bernard, Ric T F , Nurton, Jane P
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447245 , vital:74599 , https://www.ajol.info/index.php/az/article/view/154234
- Description: Relative brain size (size of the brain once body size effects have been removed) has been calculated for 16 species of rodent from South Africa and is shown to vary with six species having a positive RBS (that is a brain larger than expected) and 10 a negative RBS. Arboreal species such as Paraxerus cepapi and Graphiurus murinus and omnivores (G. murinus) have relatively larger brains than do the fossoriai root eaters such as Cryptomys hottentotus and terrestrial follivores (Otomys irroratus). It is suggested that the relatively large brains can be linked to the complex behavioural patterns necessary for locomotion in three dimensions and for utilization of a food resource such as insects that is randomly distributed in time and space. The three sciuromorph rodents (Xerus inauris, Paraxerus cepapi and Pedetes capensis) have very different life styles but all have a positive RBS and it is suggested that a relatively large brain may be a characteristic of the suborder.
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Insect herbivores on the exotic weeds Solanum elaeagnifolium Cavanilles and S. sisymbriifolium Lamarck (Solanaceae) in South Africa
- Authors: Hill, Martin P , Hulley, Patrick E , Olckers, T
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451454 , vital:75050 , https://hdl.handle.net/10520/AJA10213589_58
- Description: In South Africa, the weeds Solanum elaeagnifolium Cavanilles and S. sisymbriifolium Lamarck (Solanaceae) sustain little observable damage from herbivorous insects. Relatively few insect species occur on these plants and at low individual densities. Since native insects are not important in the natural control of S. elaeagnifolium and S. sisymbriifolium, additional agents should be imported for the biological control of these weeds. The absence of important local herbivores means that the possibility of interaction between these and potential biological control agents need not be a consideration in choosing the agents. The nature and numbers of the insect herbivores of S. elaeagnifolium and S. sisymbriifolium are compared with those on another solanaceous weed, S. mauritianum Scopoli, and on native Solanum species. These insect species are discussed relative to plant defence mechanisms.
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Interaction of cyanide with iron (II) phthalocyanine
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295497 , vital:57347 , xlink:href="https://doi.org/10.1039/DT9930003601"
- Description: The kinetics and equilibria for the reaction between cyanide and iron (II) phthalocyanine [Fe(pc)](H2pc = phthalocyanine) in dimethyl sulfoxide (dmso) were studied at 25 °C. The complex [Fe(pc)(CN)2]2– is formed in two consecutive pseudo-first-order processes with k2f= 17.5 ± 0.8 dm3 mol–1 s–1 and k3f= 0.20 ± 0.05 dm3 mol–1 s–1, where k2f and k3f are the rate constants for the binding of the first and second cyanide ligands, respectively. The equilbrium constants were fund to be K2= 3.0 × 103 dm3 mol–1 and K3= 5.7 × 102 dm3 mol–1, for the formation of [Fe(pc)(CN)(dmso)]– and [Fe(pc)(CN)2]2–, respectively.
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Kinetics of the reaction of cyanide with ruthenium phthalocyanine complexes
- Authors: Nyokong, Tebello , Guthrie-Strachan, Jeffry
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295509 , vital:57348 , xlink:href="https://doi.org/10.1016/S0020-1693(00)85128-2"
- Description: Kinetic studies of the reaction of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc in DMF are reported. In the presence of a large excess of cyanide, the (CN)2RuPc complex is formed by pseudo first order kinetics. The reaction is first order in both cyanide and phthalocyanine, with specific rate constants of 5.2×10−2 and 7.2×10−2 M−1 s−1 for reactions of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc, respectively. The rate constants correspond to the coordination of the second cyanide ligand to the ruthenium phthalocyanine species.
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Larval development of Gilchristella aestuaria (Gilchrist, 1914)(Pisces: Clupeidae) from southern Africa
- Authors: Haigh, Eliria H , Whitfield, Alan K
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447533 , vital:74654 , https://hdl.handle.net/10520/AJA00445096_482
- Description: The larval development of the southern African endemic clupeid Gilchristella aestuaria is descriptionbed and illustrated from specimens collected in the Swartvlei and Sundays estuarine systems of the Cape Province. Free embryos have no visible gut, unpigmented eyes and bodies, and are dependent on the yolk sac contents for nutrnion. This stage lasts until about 4 mm body length (BL) when the eyes become pigmented and a gut becomes visible. Between 4 mm and 7 mm BL melanophores on the ventral aspect of the body form. and the dorsal and caudal fin anlagen develop. Between 7 mm and 8 mm BL the swimbladder forms, flexion occurs and the anal fin anlage develops. By the to mm BL stage most of the skeletal elements have begun to differentiate, with the vertebral centra already showing signs of ossification. General ossification commences between t 2 mm and 13 mm BL. All unpaired fins have the adult complement of rays by 15 mm BL. Scalation starts between 16 mm and 17 mm BL and is complete by 20 mm BL. Body depth increases gradually. from about 5% of BL in the early larval stages to >14% of BL in the juveniles. The pre-anal length decreases from about 87% of BL in the larvae to approximately 69% of BL in the juveniles. Head length increases from approximately 11 % of BL in the larvae to 24-29% of BL in the juveniles. The larval snout is initially 2% of BL, increasing to 7% of BL in the juvenile stages owing to the development of jaw elements.
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The nature of the oxidation products of dicyanoruthenium phthalocyanine in aqueous and non-aqueous solvents
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295543 , vital:57352 , xlink:href="https://doi.org/10.1016/S0277-5387(00)81741-6"
- Description: The cyclic voltammetry of [(CN)2RuIIPc]2− in acetonitrile or dichloromethane shows two oxidation couples at E12 = 0.31 and 0.85 V (vs S.C.E.) in CH2Cl2 and E12 = 0.45 and 1.15 V (vs S.C.E.) in acetonitrile. The spectroelectrochemistry of [(CN)2RuIIPc]2− in these solvents showed that oxidations occur at the phthalocyanine ligand. K2[(CN)2RuIIPc] dissolves in water at pHs greater than 5. The cyclic voltammetry of this complex showed oxidation couples at 0.32 and 0.29 V (vs S.C.E.) for aqueous solutions containing sodium sulphate (0.1M) and for buffered solutions (pH = 9), respectively. Both cyclic voltammetry and controlled potential coulometry gave evidence of electrocrystallization of the oxidation product. Chemical oxidations of [(CN)2RuIIPc]2− in water also showed phthalocyanine ligand oxidation.
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The occurrence and development of' Siamese twins' and other abnormalities in Oreochromis mossambicus (Pisces, Cichlidae).
- Authors: Holden, Kathleen K , Bruton, Michael N
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447288 , vital:74602 , https://hdl.handle.net/10520/AJA00445096_605
- Description: Specimens from a clutch of Oreochromis mossambicus (Pisces, Cichlidae) exhibited a number of abnormalities such as enlarged pericardia, thin tube-like hearts, large depressions in the yolksac, spinal deformities and twinning. Descriptions of the differences in early ontogeny of two pairs of 'Siamese twins' over a period of at least eight days are given. The developmental pattern of the twins is similar to that of normal specimens but the developmental rate is slower in the twins. Possible explanations for these occurrences of polyembryony are given.
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The taxonomie status of Apogon enigmaticus Smith, 1961 (Teleostei, Apogonidae)
- Authors: Gon, Ofer
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447304 , vital:74603 , https://www.ajol.info/index.php/az/article/view/154224
- Description: The validity of the cardinal fish species Apogon enigmaticus, described by Smith (1961) from a single specimen, is reassessed in view of a recent discovery of a second specimen of this species, collected by Smith, in the JLB Smith Institute of Ichthyology. Both fish were re-identified as specimens of A. apogonides (Bleeker, 1856) on the basis of dentition, pigmentation, and counts of pectoral-fin rays, gill rakers and predorsal scales. A. enigmaticas is therefore regarded as a junior synonym of A. apogonides.
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