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Towards a GPS-based TEC prediction model for Southern Africa with feed forward networks

  • Authors: Habarulema, John B , McKinnell, Lee-Anne , Opperman, Ben D L
  • Date: 2009
  • Language: English
  • Type: text , Article
  • Identifier: vital:6806 , http://hdl.handle.net/10962/d1004192
  • Description: In this paper, first results from a national Global Positioning System (GPS) based total electron content (TEC) prediction model over South Africa are presented. Data for 10 GPS receiver stations distributed through out the country were used to train a feed forward neural network (NN) over an interval of at most five years. In the NN training, validating and testing processes, five factors which are well known to influence TEC variability namely diurnal variation, seasonal variation, magnetic activity, solar activity and the geographic position of the GPS receivers were included in the NN model. The database consisted of 1-min data and therefore the NN model developed can be used to forecast TEC values 1 min in advance. Results from the NN national model (NM) were compared with hourly TEC values generated by the earlier developed NN single station models (SSMs) at Sutherland (32.38°S, 20.81°E) and Springbok (29.67°S, 17.88°E), to predict TEC variations over the Cape Town (33.95°S, 18.47°E) and Upington (28.41°S, 21.26°E) stations, respectively, during equinoxes and solstices. This revealed that, on average, the NM led to an improvement in TEC prediction accuracy compared to the SSMs for the considered testing periods.
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  • Date Issued: 2009

First steps in the development of a water temperature model framework for refining the ecological Reserve in South African rivers

  • Authors: Rivers-Moore, Nick A , Hughes, Denis A , Mantel, Sukhmani K , Hill, Trevor R
  • Date: 2008-10-05
  • Language: English
  • Type: text , Article
  • Identifier: vital:7092 , http://hdl.handle.net/10962/d1012425
  • Description: Ecological Reserve determination for rivers in South Africa presently does not include a water temperature component, in spite of its importance in determining species distribution patterns. To achieve this requires an understanding of how lotic thermographs from South African rivers differ from northern hemisphere rivers, to avoid mismanaging rivers based on incorrect regional assumptions. Hourly water temperatures from 20 sites in four river systems, representing a range of latitudes, altitudes and stream orders, were assessed using a range of metrics. These data were analysed using principal component analyses and multiple linear regressions to understand what variables a water temperature model for use in ecoregions within South Africa should include. While temperature data are generally lacking in low- and higher-order South African rivers, data suggest that South African rivers are warmer than northern hemisphere rivers. Water temperatures could be grouped into cool, warm and intermediate types. Based on temperature time series analyses, this paper argues that a suitable water-temperature model for use in ecological Reserve determinations should be dynamic, include flow and air temperature variables, and be adaptive through a heat exchange coefficient term. The inclusion of water temperature in the determination and management of river ecological Reserves would allow for more holistic application of the National Water Act's ecological management provisions. Water temperature guidelines added to the ecological Reserve could be integrated into heuristic aquatic monitoring programmes within priority areas identified in regional conservation plans.
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  • Date Issued: 2008-10-05

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A global study of forensically significant calliphorids: implications for identification

  • Authors: Harvey, M L , Gaudieri, S , Villet, Martin H , Dadour, I R
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6863 , http://hdl.handle.net/10962/d1011156
  • Description: A proliferation of molecular studies of the forensically significant Calliphoridae in the last decade has seen molecule-based identification of immature and damaged specimens become a routine complement to traditional morphological identification as a preliminary to the accurate estimation of post-mortem intervals (PMI), which depends on the use of species-specific developmental data. Published molecular studies have tended to focus on generating data for geographically localised communities of species of importance, which has limited the consideration of intraspecific variation in species of global distribution. This study used phylogenetic analysis to assess the species status of 27 forensically important calliphorid species based on 1167 base pairs of the COI gene of 119 specimens from 22 countries, and confirmed the utility of the COI gene in identifying most species. The species Lucilia cuprina, Chrysomya megacephala, Ch. saffranea, Ch. albifrontalis and Calliphora stygia were unable to be monophyletically resolved based on these data. Identification of phylogenetically young species will require a faster-evolving molecular marker, but most species could be unambiguously characterised by sampling relatively few conspecific individuals if they were from distant localities. Intraspecific geographical variation was observed within Ch. rufifacies and L. cuprina, and is discussed with reference to unrecognised species.
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  • Date Issued: 2008

A preliminary survey of the estuaries on the south coast of South Africa, Cape St Blaize, Mossel Bay - Robberg Peninsula, Plettenberg Bay, with particular reference to the fish fauna

  • Authors: James, Nicola C , Harrison, T D
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:7141 , http://hdl.handle.net/10962/d1011834
  • Description: The coastal river systems on the south coast of South Africa from Cape St Blaize to Robberg Peninsula were surveyed during October and November 1994. The ichthyofaunal and physico-chemical characteristics of each system are presented and their suitability as estuarine nursery areas is discussed. Five systems (Rooi, Meul, Grooteiland, Kranshoek and Crooks) are outlets of small coastal streams and probably provide little or no habitat for either resident estuarine or migrant marine fishes owing to their small size. Four systems (Maalgate, Gwaing, Skaapkop and Kaaimans) are located within deeply incised valleys and have a permanent connection with the sea. The amount of marginal and intertidal habitat available to fishes, however, is limited due to their morphology. Six systems (Hartenbos, Groot Brak, Touw, Swartvlei, Goukamma and Noetsie) are intermittently open to the sea. Although the Touw and Swartvlei are connected to coastal lake systems, flow within these estuaries is not sufficient to prevent the build up of a sand barrier at the mouth. The Hartenbos, Groot Brak, Goukamma, and Noetsie are also periodically closed by a sand bar. The construction of a dam in the lower catchment of the Groot Brak has affected the hydrology of the system. The two remaining estuaries (Klein Brak and Knysna) are permanently open. In addition to strong tidal currents, the fixing of the mouth of the Knysna Estuary between rocky headlands also serves to maintain a permanent connection with the sea. Mugilidae and Sparidae were represented by the greatest number of species, and also dominated catches numerically and by mass. The fish fauna of all the estuaries surveyed were dominated by the juveniles of estuarine-dependent marine species and estuarine-resident species were also well represented in catches. The estuaries surveyed provide a vital habitat for both marine migrant species and resident species, most of which are endemic to the region.
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  • Date Issued: 2008

Application of satellite-derived rainfall estimates to extend water resource simulation modelling in South Africa

  • Authors: Sawunyama, Tendai , Hughes, Denis A
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:7089 , http://hdl.handle.net/10962/d1012419
  • Description: Spatially interpolated rainfall estimates from rain-gauges are widely used as input to hydrological models, but deriving accurate estimates at appropriate space and time scales remain a major problem. In South Africa there has been a gradual decrease in the number of active rain-gauges over time. Satellite-based estimates of spatial rainfall are becoming more readily available and offer a viable substitute. The paper presents the potential of using Climate Prediction Center African daily precipitation climatology (CPCAPC) satellite-based datasets (2001-2006) to drive a Pitman hydrological model which has been calibrated using gauge-based rainfall data (1920-1990). However, if two sources of rainfall data are to be used together, it is necessary to ensure that they are compatible in terms of their statistical properties. A non-linear frequency of exceedance transformation technique was used to correct the satellite data to be more consistent with historical spatial rainfall estimates. The technique generated simulation results for the 2001 to 2006 period that were greatly improved compared to the direct use of the untransformed satellite data. While there remain some further questions about the use of satellite-derived rainfall data in different parts of the country, they do seem to have the potential to contribute to extending water resource modelling into the future.
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  • Date Issued: 2008

Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary

  • Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, Alan K
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
  • Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
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  • Date Issued: 2008

Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater

  • Authors: Barber-James, Helen M , Gattolliat, J-L , Sartori, Michel , Hubbard, Michael D
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6895 , http://hdl.handle.net/10962/d1011655
  • Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
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  • Date Issued: 2008

Lattice-valued convergence spaces and regularity

  • Authors: Jäger, Gunter
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6826 , http://hdl.handle.net/10962/d1012336
  • Description: We define a regularity axiom for lattice-valued convergence spaces where the lattice is a complete Heyting algebra. To this end, we generalize the characterization of regularity by a ”dual form” of a diagonal condition. We show that our axiom ensures that a regular T1-space is separated and that regularity is preserved under initial constructions. Further we present an extension theorem for a continuous mapping from a subspace to a regular space. A characterization in the restricted case that the lattice is a complete Boolean algebra in terms of the closure of an L-filter is given.
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  • Date Issued: 2008

Rhodes professor among best women scientists

  • Authors: Ndabeni, Khanyi
  • Date: 2008
  • Subjects: Nyokong, Tebello
  • Language: English
  • Type: Article , text
  • Identifier: vital:7186 , http://hdl.handle.net/10962/d1006278 , Nyokong, Tebello
  • Description: A RHODES University scientist's ground breaking work in harnessing light for cancer therapy has won her a United Nations award worth almost R1- million. Named on Monday by the UN Educational, Scientific and Cultural Organisation (Unesco) as one of the world's top five "Exceptional Women Scientists", Professor Tebello Nyokong said winning the award was "just like getting a Nobel Prize". She was also recognised for her work regarding environmental cleanups. Nyokong, 57, grew up herding sheep in Lesotho and was unable to afford shoes. She now works in Rhodes University's chemistry department. She won the award for the Africa and Arab states category on World Science Day, which took place on Monday.
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  • Date Issued: 2008

SA scientist one of the top five female physical scientists

  • Authors: Limson, Janice L
  • Date: 2008
  • Subjects: Nyokong, Tebello
  • Language: English
  • Type: Article , text
  • Identifier: vital:7189 , http://hdl.handle.net/10962/d1006283 , http://www.scienceinafrica.co.za/2008/october/nyokong.htm
  • Description: South African scientist Professor Tebello Nyokong scoops 2009 L’ORÉAL-UNESCO For Women in Science Award. Announced on November 10, South African scientist Professor Tebello Nyokong has become the first South African scientist to win the L’ORÉALUNESCO award for women in science for research in physical sciences.
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  • Date Issued: 2008

Social Services and Benefits

  • Authors: Kruuse, Helen
  • Date: 2008
  • Language: English
  • Type: Article , text
  • Identifier: http://hdl.handle.net/10962/54211 , vital:26405 , https://store.lexisnexis.co.za/products/family-law-service-skuZASKUPG642
  • Description: Family Law Service is a subscription based product including both the printed loose-leaf and LexisMobile publications. Updates for 12 months (print and mobile) are included in the price. Family Law Service covers aspects of law pertaining to the family, including domestic violence, the Law of Islam, same- sex life partnerships, the effects of the Children's Act, 2008 and anti-trafficking law in South Africa. Family Law Service is maintained in three volumes with commentary and legislation, and with two service issues published a year.
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  • Date Issued: 2008

Sterols and sterolins in Hypoxis hemerocallidea (African potato)

  • Authors: Nair, V D P , Kanfer, Isadore
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6417 , http://hdl.handle.net/10962/d1006535
  • Description: Commercially available health supplements and herbal remedies containing sterols and sterolins, either from African potato (Hypoxis hemerocallidea) alone, or whether enriched with sterols and sterolins, are claimed to be efficacious in the treatment of a variety of ailments. Sterols and sterolins in African potato are purported to be the relevant constituents that are required for the therapeutic claims of such products. A patent describing the extraction of sterolins from African potato plant material has claimed that approximately 9 mg sterolins can be isolated from 100 g of an enriched aqueous African potato extract. Our analysis of African potato plant material and its sterol and sterolin content, when similarly prepared, shows that the measureable content of sterols and sterolins in African potato is far less than the amounts of these compounds that have been claimed to be necessary for therapeutic benefit. We conclude that therapeutic claims relating to sterol and sterolin content in African potato are unsubstantiated, in view of the extremely low content of such compounds that we have isolated from our plant material, and in products containing African potato, or extracts thereof.
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  • Date Issued: 2008

Temporal and spatial variability in stable isotope ratios of SPM link to local hydrography and longer term SPM averages suggest heavy dependence of mussels on nearshore production

  • Authors: Hill, Jaclyn M , McQuaid, Christopher D , Kaehler, Sven
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6969 , http://hdl.handle.net/10962/d1012034
  • Description: Temporal changes in hydrography affect suspended particulate matter (SPM) composition and distribution in coastal systems, potentially influencing the diets of suspension feeders. Temporal variation in SPM and in the diet of the mussel Perna perna, were investigated using stable isotope analysis. The δ13C and δ15 N ratios of SPM, mussels and macroalgae were determined monthly, with SPM samples collected along a 10 km onshore–offshore transect, over 14 months at Kenton-on-Sea, on the south coast of South Africa. Clear nearshore (0 km) to offshore (10 km) carbon depletion gradients were seen in SPM during all months and extended for 50 km offshore on one occasion. Carbon enrichment of coastal SPM in winter (June–August 2004 and May 2005) indicated temporal changes in the nearshore detrital pool, presumably reflecting changes in macroalgal detritus, linked to local changes in coastal hydrography and algal seasonality. Nitrogen patterns were less clear, with SPM enrichment seen between July and October 2004 from 0 to 10 km. Nearshore SPM demonstrated cyclical patterns in carbon over 24-h periods that correlated closely with tidal cycles and mussel carbon signatures, sampled monthly, demonstrated fluctuations that could not be correlated to seasonal or monthly changes in SPM. Macroalgae showed extreme variability in isotopic signatures, with no discernable patterns. IsoSource mixing models indicated over 50% reliance of mussel tissue on nearshore carbon, highlighting the importance of nearshore SPM in mussel diet. Overall, carbon variation in SPM at both large and small temporal scales can be related to hydrographic processes, but is masked in mussels by long-term isotope integration.
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  • Date Issued: 2008

The oppression of isiXhosa literature and the irony of transformation

  • Authors: Kaschula, Russell H
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:6334 , http://hdl.handle.net/10962/d1012398 , https://orcid.org/0000-0002-5481-6748
  • Description: his article will contend that the natural development of isiXhosa orature and literature, as with all South African indigenous literatures, ended with the arrival of European missionaries in 1799. The apartheid policy then exacerbated the destructive approaches to indigenous languages already in operation as it designated separate language boards for language development. These boards operated in the 'homelands' and were generally conservative, corrupt and oppressive. The manuscripts they recommended to publishers were for the most part only those that could be prescribed in schools. This resulted in the publishing of material that was parochial, apolitical and neutral in style. Often the material prescribed was written by the board members themselves. For instance, Lennox Sebe, erstwhile President of the Ciskei, produced an isiXhosa book entitled Ucamngco, for prescription, though it seems to contain little original material. Laurence Wright has shown that the opposite was true for English literature written by black South Africans and published internationally in the 1970s, at the height of apartheid (2004, 47). He describes, for instance, how one of the manuscript readers of Peteni's seminal novel, Hill of Fools (1976), rejected it as irrelevant and unsuitable for publication precisely because it made no reference to South Africa's turbulent politics. Throughout this period, however, only apolitical novels were published in the indigenous languages.
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  • Date Issued: 2008

Towards revised physically based parameter estimation methods for the Pitman monthly rainfall-runoff model

  • Authors: Kapangaziwiri, Evison , Hughes, Denis A
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:7088 , http://hdl.handle.net/10962/d1012417
  • Description: This paper presents a preliminary stage in the development of an alternative parameterisation procedure for the Pitman monthly rainfall runoff model which enjoys popular use in water resource assessment in Southern Africa. The estimation procedures are based on the premise that it is possible to use physical basin properties directly in the quantification of the soil moisture accounting, runoff, and recharge and infiltration parameters. The results for selected basins show that the revised parameters are at least as good as current regionalised sets or give satisfactory results in areas where no regionalised parameters exist.
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  • Date Issued: 2008

Winds of change in teachers’ classroom assessment practice: a self-critical reflection on the teaching and learning of visual literacy in a rural Eastern Cape High School

  • Authors: Mbelani, Madeyandile
  • Date: 2008
  • Language: English
  • Type: text , Article
  • Identifier: vital:7021 , http://hdl.handle.net/10962/d1007201
  • Description: The year 2006 saw the implementation of a new curriculum for teaching English First Additional Language (FAL) in grades 10-12 in South African high schools. The curriculum includes the teaching and assessment of visual literacy – a challenge for teachers whose apartheid-era teacher education did not address visual literacy at all. The article is a self-critical reflection on my attempts to teach and assess a unit on visual literacy in a Grade 10 class in a rural high school in the Eastern Cape province of South Africa.
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  • Date Issued: 2008

Women writers of the South Asian diaspora : towards a transnational feminist Aesthetic?

  • Authors: Naidu, Samantha
  • Date: 2008
  • Language: English
  • Type: Article , text
  • Identifier: vital:26375 , http://hdl.handle.net/10962/54027 , https://orcid.org/0000-0001-9456-8657
  • Description: Women writers of the South Asian diaspora have, in recent decades, found prominence in the international literary arena. These writers may be new immigrants to their diasporic homes, migrants who divide their lives between far-flung homes (for example, Anita Desai, who lives in India, the United Kingdom [UK] and Germany), or descended from nineteenth-century immigrants, as is the case of South African authors like Farida Karodia and Agnes Sam.
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  • Date Issued: 2008

The Educational Journal

  • Date: 2007-09
  • Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
  • Language: English
  • Type: text , Article
  • Identifier: http://hdl.handle.net/10948/41209 , vital:36401 , Bulk File 7
  • Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
  • Full Text: false
  • Date Issued: 2007-09

The Educational Journal

  • Date: 2007-03
  • Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
  • Language: English
  • Type: text , Article
  • Identifier: http://hdl.handle.net/10948/41189 , vital:36399 , Bulk File 7
  • Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
  • Full Text: false
  • Date Issued: 2007-03
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