Automated estimation and analyses of meteorological drought characteristics from monthly rainfall data
- Authors: Smakhtin, V U , Hughes, Denis A
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:7078 , http://hdl.handle.net/10962/d1009746
- Description: The paper describes a new software package for automated estimation, display and analyses of various drought indices – continuous functions of precipitation that allow quantitative assessment of meteorological drought events to be made. The software at present allows up to five different drought indices to be estimated. They include the Decile Index (DI), the Effective Drought Index (EDI), the Standardized Precipitation Index (SPI) and deviations from the long-term mean and median value. Each index can be estimated from point and spatially averaged rainfall data and a number of options are provided for months' selection and the type of the analysis, including a running mean, single value or multiple annual values. The software also allows spell/run analysis to be performed and maps of a specific index to be constructed. The software forms part of the comprehensive computer package, developed earlier and designed to perform the multitude of water resources analyses and hydro-meteorological data processing. The 7-step procedure of setting up and running a typical drought assessment application is described in detail. The examples of applications are given primarily in the specific context of South Asia where the software has been used.
- Full Text:
- Date Issued: 2007
Bee-hawking by the wasp, Vespa velutina, on the honeybees Apis cerana and A. mellifera
- Authors: Tan, K , Radloff, Sarah E , Li, J J , Hepburn, H Randall , Yang, Ming-Xian , Zhang, L J , Neumann, Peter
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6941 , http://hdl.handle.net/10962/d1011965
- Description: The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively.
- Full Text:
- Date Issued: 2007
Conserving pattern and process in the Southern Ocean: designing a Marine Protected Area for the Prince Edward Islands
- Authors: Lombard, A T , Reyers, B , Schonegevel, L Y
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:7140 , http://hdl.handle.net/10962/d1011822
- Description: South Africa is currently proclaiming a Marine Protected Area (MPA) in the Exclusive Economic Zone (EEZ) of its sub-Antarctic Prince Edward Islands. The objectives of the MPA are to: 1) contribute to a national and global representative system of MPAs, 2) serve as a scientific reference point to inform future management, 3) contribute to the recovery of the Patagonian toothfish (Dissostichus eleginoides), and 4) reduce the bird bycatch of the toothfish fishery, particularly of albatrosses and petrels. This study employs systematic conservation planning methods to delineate a MPA within the EEZ that will conserve biodiversity patterns and processes within sensible management boundaries, while minimizing conflict with the legal toothfish fishery. After collating all available distributional data on species, benthic habitats and ecosystem processes, we used C-Plan software to delineate a MPA with three management zones: four IUCN Category Ia reserves (13% of EEZ); two Conservation Zones (21% of EEZ); and three Category IV reserves (remainder of EEZ). Compromises between conservation target achievement and the area required by the MPA are apparent in the final reserve design. The proposed MPA boundaries are expected to change over time as new data become available and as impacts of climate change become more evident.
- Full Text:
- Date Issued: 2007
Neural network-based prediction techniques for global modeling of M(3000)F2 ionospheric parameter
- Authors: Oyeyemi, E O , McKinnell, Lee-Anne , Poole, Allon W V
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6803 , http://hdl.handle.net/10962/d1004166
- Description: In recent times neural networks (NNs) have been employed to solve many problems in ionospheric predictions. This paper illustrates a new application of NNs in developing a global model of the ionospheric propagation factor M(3000)F2. NNs were trained with daily hourly values of M(3000)F2 from various ionospheric stations spanning the period 1964–1986 with the following temporal and spatial input parameters: Universal Time, geographic latitude, magnetic inclination, magnetic declination, solar zenith angle, day of the year, A16 index (a 2-day running mean of the 3-h planetary magnetic ap index), R2 index (a 2-month running mean of sunspot number), and the angle of meridian relative to the subsolar point. The performance of the NNs was verified by comparing the predicted values of M(3000)F2 with observed values from a few selected ionospheric stations and the IRI (International Reference Ionosphere) model (CCIR M(3000)F2 model) predicted values. The results obtained compared favourably with the IRI model. Based on the error differences, the result obtained justifies the potential of the NN technique for the predictions of M(3000)F2 values on a global scale.
- Full Text:
- Date Issued: 2007
Olive Schreiner in Rhodesia: an episode in a biography
- Authors: Walters, Paul S , Fogg, W Jeremy M
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6123 , http://hdl.handle.net/10962/d1004707
- Description: Readers of biographies of Olive Schreiner - except for the pioneering work of Vera Buchanan-Gould (see 1948, 198-99) - could be forgiven for doubting whether Olive Schreiner ever was in Rhodesia. Although her husband's edition of her Letters includes three which cover this journey (Cronwright-Schreiner 1924a), he makes no mention of it in his Life (1924), and it is not touched on either in First and Scott (1980) or in Stanley's impressive biographical chapter (2002). Arguably, it does nothing to alter the by now well-established outlines of Olive Schreiner's life; yet, as we shall see, the visit itself might have meant the premature end of that life. Moreover, it documents Schreiner's visit to two sites of immense importance to her : the 'Hanging Tree' in Bulawayo which features in the (deliberately shocking) photographic frontispiece to the first edition of Trooper Peter Halket of Mashonaland (1897), and, secondly, Cecil Rhodes's grave in the Matopos. In just over a decade (13 Aug. 1921), she too would lie in her chosen mountaintop tomb.
- Full Text:
- Date Issued: 2007
Pretopological and topological lattice-valued convergence spaces
- Authors: Jäger, Gunter
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6827 , http://hdl.handle.net/10962/d1012337
- Description: We show that the classical axiom which characterizes pretopological convergence spaces splits into two axioms in the general Heyting algebra-valued case. Furthermore we present a generalization of Kowalski’s diagonal condition to the lattice-valued case.
- Full Text:
- Date Issued: 2007
Recovery of the critically endangered river pipefish, Syngnathus watermeyeri, in the Kariega Estuary, Eastern Cape province
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6965 , http://hdl.handle.net/10962/d1012028
- Description: An intensive ichthyofaunal survey in the permanently open Kariega Estuary along the Eastern Cape coast has identified a breeding population of the critically endangered river pipefish, Syngnathus watermeyeri, within the middle and upper reaches of the system. This is the first recorded capture of this species in the estuary for over four decades. We suggest that the presence of S. watermeyeri is the result of the heavy rainfall within the region, which contributed to the establishment of optimum habitat requirements (mesohaline conditions and increased food availability) of the pipefish.
- Full Text:
- Date Issued: 2007
South African research in the hydrological sciences : 2003 -2006 : IUGG report
- Authors: Hughes, Denis A
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:7087 , http://hdl.handle.net/10962/d1012415
- Description: The principal activities of South African researchers in hydrology and water resources during the reporting period have been concerned with ground- and surface-water interactions, rainfall-runoff modelling, the establishment of improved regional water resource databases, the ecological Reserve, and investigating the likely consequences of climate change. Most of these studies have a strong emphasis on supporting the provisions of the National Water Act of 1998. Research programmes are benefiting from international and regional cooperation. In contrast, the lack of young scientists entering the field poses the greatest threat to hydrological research in South Africa.
- Full Text:
- Date Issued: 2007
The effect of physico-chemical parameters and chemical compounds on the activity of β-d-galactosidase (B-GAL), a marker enzyme for indicator microorganisms in water
- Authors: Wutor, V C , Togo, C A
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6470 , http://hdl.handle.net/10962/d1005800 , https://doi.org/10.1016/j.chemosphere.2007.02.050
- Description: The presence of coliforms in polluted water was determined enzymatically (in situ) by directly monitoring the activity of beta-d-galactosidase (B-GAL) through the hydrolysis of the yellow chromogenic subtrate, chlorophenol red beta-d-galactopyranoside (CPRG), which produced a red chlorophenol red (CPR) product. The objectives of this study were to monitor the effect of compounds commonly found in the environment and used in water treatment on a B-GAL CPRG assay and to investigate the differences between the environmental B-GAL enzyme and the pure commercial enzyme. Environmental B-GAL was optimally active at pH 7.8. Two temperature optima were observed at 35 and 55 degrees C, respectively. B-GAL activity was strongly inhibited by silver and copper ions. While calcium and ferrous ions at lower concentrations (50-100mgl(-1)) increased the enzyme activity, a reduction was observed at higher concentrations (200mgl(-1)). Sodium hypochlorite, normally used in rural areas to disinfect water gradually decreased B-GAL activity at concentrations between 0 and 5600ppm for both the commercial and environmental enzymes. B-GAL from the environment behaved differently from its commercially available counterpart.
- Full Text:
- Date Issued: 2007
The effects of buffer molarity, agitation rate and mesh size on verapamil release from modified release mini-tablets using USP Apparatus 3
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6386 , http://hdl.handle.net/10962/d1006307
- Description: The effects of agitation rate, buffer molarity,and mesh size on the dissolution rate of verapamil hydrochloride from sustained release matrix tablets were studied using USP Apparatus 3. Eudragit® and Carbopol® were used as rate-retarding polymers in tablets prepared by wet granulation.The study was conducted to determine whether the drugs exhibit similar release characteristics when tested under the same dissolution conditions. It was found that the dissolution rate of verapamil hydrochloride was affected by the variables assessed in these studies.
- Full Text:
- Date Issued: 2007
The Emerging Role of ubuntu-botho in Developing a Consensual South African Legal Culture
- Authors: Kruuse, Helen , Midgley, Rob
- Date: 2007
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54224 , vital:26413 , https://dspace.library.uu.nl/handle/1874/27652
- Description: Legal culture in apartheid South Africa has variously been described as conservative and positivist, with judicial deference to the executive and to parliamentary sovereignty; formalistic, technical and authoritarian; and ‘of reasoned argument’ and justification. Until 1994, law drew its legitimacy from the very fact that it was state sanctioned, and the material context or the social aftermath of the application of a rule was in many instances deemed irrelevant. However, the adoption, first, of the interim Constitution, and later the final Constitution, saw a desire to transform this legal culture. The Constitution is now more than a formal document regulating public power: it also embodies a normative value system in terms of which judges are called upon to interpret laws and their application.
- Full Text:
- Date Issued: 2007