A digital watermarking scheme for Bezier surfaces
- Authors: Chadwick, J , Bangay, Shaun D , Wentworth, Peter E
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432769 , vital:72898 , https://www.cs.ru.ac.za/research/groups/vrsig/pastprojects/046watermarking/paper01.pdf
- Description: Owners and vendors are increasingly publishing their materials in digital form. Because such materials can be exactly copied, a mechanism is required that will protect the legitimate owners of these works, by providing proof of original ownership. Digital watermarking has now become one accepted method of establishing ownership of digital materials. The owner of a work embeds a pattern, called a digital watermark, in the content. This embedded watermark is normally undetectable, but its presence can be demonstrated by the owner of the work or his agent, thereby proving ownership. Digital watermarking has been used for many types of multimedia content, primarily audio, video and flat images. Recently, interest has been shown in applying digital watermarking schemes to 3D surfaces, in various formats. In this paper, we examine a method whereby a digital watermark can be embedded in a Bezier surface. A prototype watermarking method for such surfaces is presented, with some experimental results, and a discussion of directions for future research.
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- Date Issued: 2003
A lightwave 3d plug-in for modeling long hair on virtual humans
- Authors: Patrick, Deborah , Bangay, Shaun D
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432953 , vital:72916 , https://doi.org/10.1145/602330.602360
- Description: Multimedia applications today make use of virtual humans. Generating realistic virtual humans is a challenging problem owing to a number of factors, one being the simulation of realistic hair. The difficulty in simulating hair is due to the physical properties of hair. The average human head holds thousands of hairs, with the width of each hair often smaller than the size of a pixel. There are also complex lighting effects that occur within hair. This paper presents a LightWave 3D plug-in for modeling thousands of individual hairs on virtual humans. The plug-in allows the user to specify the length, thickness and distribution of the hair, as well as the number of segments a hair is made up of. The plug-in is able to add hairs to a head model, which the user then modifies to define a hairstyle. The hairs are then multiplied by the plug-in to produce many hairs. By providing a plug-in that does most of the work and produces realistic results, the user is able to produce a hairstyle without modeling each individual strand of hair. This greatly reduces the time spent on hair modeling, and makes the possibility of adding realistic long hair to virtual humans reasonable.
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- Date Issued: 2003
A note on mapping propolis deposits in Cape honey bee (Apis mellifera capensis) colonies
- Authors: Ellis, James D , Hepburn, H Randall
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451805 , vital:75078 , https://hdl.handle.net/10520/EJC32532
- Description: Propolis is a mixture of plant-derived substances, and sometimes wax, collected by most Apis mellifera subspecies for use as caulking and entrance-reducing material and as a colony sealant and sterilant (Ruttner 1988; Schmidt and Buchmann 1992; Hepburn and Radloff 1998). Additionally, it is used in honey bee defense against colony invaders, particularly Aethina tumida Murray (small hive beetles) (Hepburn and Radloff 1998; Neumann et al. 2001; Ellis 2002).
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- Date Issued: 2003
A solution community: ways that work: useful solutions
- Authors: du Toit, Peter
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/454623 , vital:75360 , https://hdl.handle.net/10520/EJC146301
- Description: It begins in the Southern African country of Zambotswa in a place called Anytown. Population: 540 000. The owner-editor of the Anytown Farmers' Weekly (AFW) has died and the Big Media Company, with its substantial assets across the country, has bought out his struggling pa-per.
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- Date Issued: 2003
A Theoretical Framework for Professional Development in a South African University
- Authors: Quinn, Lynn
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/484164 , vital:78875 , https://doi.org/10.1080/1360144042000277946
- Description: The changing context of higher education both internationally and in South Africa has presented challenges to lecturers that have led in some institutions to the introduction of accredited professional development courses for academics. Such courses for university lecturers are relatively new in South Africa. This paper reports on research in progress on a Post Graduate Certificate in Higher Education and Training course offered at Rhodes University in South Africa. It highlights some important questions that have arisen on the ways in which the theoretical framework of the course has or has not met the needs of diverse groups of lecturers within the specific South African context. A central theme of the course is that of the critically reflective practitioner. Lecturers are encouraged to explore the ontological and epistemological underpinnings of their disciplines and to examine the philosophical assumptions of their espoused theories about teaching and learning as well as their teaching practice. The theoretical framework has been found to be most successful for more experienced academics. However, the author raises some important questions regarding the suitability of this framework in relation to the specific post‐apartheid context in which the course operates, specifically whether the course prepares lecturers to open up both “actual” and “epistemological” access to all the students at the university.
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- Date Issued: 2003
Apartheid Shakespeare On Trial: Rohan Quince. Shakespeare in South Africa: Stage Productions during the Apartheid Era: article review
- Authors: Wright, Laurence
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/455576 , vital:75440 , https://hdl.handle.net/10520/EJC48018
- Description: This is an important book for a number of reasons. First, it delineates a period of Shakespearean production in South Africa scarcely investigated. Secondly, the study takes trouble relating the productions under scrutiny to their socio-political milieu (not always successfully). And thirdly, it is written by someone who actively enjoys Shakespeare and the theatre.
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- Date Issued: 2003
Classroom talk: there are more questions than answers.
- Authors: Hendricks, Monica
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/469437 , vital:77242 , https://doi.org/10.2989/16073610309486326
- Description: Congruence between new language in education policies and broader curriculum policy is crucial if educational and language acquisition plans are to be realised, and wider social aims of access and equity are to be met. This study addresses the alignment between the language policy choice of Vuka primary school, and the classroom practices of an English and a Science teacher. My research interests were (i) to analyse classroom talk with respect to teachers' questions providing comprehensible input (Krashen, 1982) and learners' responses constituting comprehensible output (Swain, 1985); (ii) to establish whether there was congruence between national language in education policy (LiEP) and curriculum policy, on the one hand, and local school-level language policy and practices, on the other. My findings provide empirical evidence of alignment between the language policy of Vuka primary and the classroom language practices of an English and a Science teacher in Grades 5, 6 and 7.
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- Date Issued: 2003
Crystallographic Analysis and Structural Revision of a Spiroterpenoid Rearrangement Product
- Authors: Lobb, Kevin A , Kaye, Perry T
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449335 , vital:74812 , xlink:href="https://www.ajol.info/index.php/sajc/article/view/122435"
- Description: Single crystal X-ray analysis of a spiroterpenoid rearrangement product has revealed that its structure is, in fact, isomeric with the structure proposed previously – an observation that has significant mechanistic implications.
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- Date Issued: 2003
Direct-use value of smallholder crop production in a semi-arid rural South African village
- Authors: Dovie, Delali B K , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181595 , vital:43750 , xlink:href="https://doi.org/10.1016/S0308-521X(02)00124-5"
- Description: The monetary value of natural resources used by rural communities for subsistence is important when addressing issues affecting the livelihoods of impoverished rural households. There is therefore the need to attribute monetary values to non-marketed products from smallholder production systems in order to reliably account for resource availability and usage to further sound policy decisions. The objective of this paper is to present an empirical analysis of the direct-use and traded values of crop production by households, and to discuss the implications for policy development. The study was undertaken in combination with an evaluation of other livelihood sectors in Thorndale, a semi-arid rural village in the Limpopo province of South Africa. The net direct-use value of crops was estimated at $443.4 per household per annum across the village. Maize (Zea mays), watermelon (Citrullus, vulgaris), peanuts (Arachis hypogaea) and common beans (Phaseolus vulgaris) contributed over 90% to the total direct-use value of crops. Maize alone contributed 40% of this value per household at an estimated $652/ha. Marketing of resources was not a common practice, limited to only maize and peanuts. Farming was basically a rain-fed–mixed cropping system with low production inputs. Farmer support services, human capital development and tenure security were major areas identified for policy development.
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- Date Issued: 2003
Dynamic run-time application development using CORBA objects and XML in the field of distributed GIS
- Authors: Preston, Michael , Clayton, Peter G , Wells, George C
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430500 , vital:72695 , https://doi.org/10.1080/1365881021000026557
- Description: The research presented describes our approach to enabling content developers and end-users to create and/or customise distributed GIS applications dynamical-ly at run-time through the incorporation of GIS services, implemented as stand-alone components or CORBA Objects, with a specialised XML descriptor. It also looks at some of the design considerations that must be dealt with by both the client-application developer as well as the service developer, including the GIS service description, associated GUI and help system.
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- Date Issued: 2003
Electrochemical behavior and detection of dopamine and ascorbic acid at an iron (II) tetrasulfophthalocyanine modified carbon paste microelectrode
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290279 , vital:56735 , xlink:href="https://doi.org/10.1002/elan.200390104"
- Description: In this article the electrocatalytic behavior of an iron(II)tetrasulfophthalocyanine modified carbon paste microelectrode for the oxidation of dopamine (DA) and ascorbic acid (AA) is described. Although the oxidation potential of ascorbic acid is shifted by over 100 mV to more positive potentials, no peak separation could be obtained. This can be explained by the immediate homogeneous reduction of the oxidation product of dopamine by ascorbic acid in solution. However, this reaction induces a shift of the half-wave potential as a function of ratio of concentration of dopamine to ascorbic acid (cDA/cAA). Therefore it was possible to determine the cAA and cDA from this potential shift and the experimental peak current. Detection limits of 4.5±0.2×10−7 and 7.5±0.5×10−7 mol L−1 were obtained respectively for dopamine and ascorbic acid for cDA/cAA>0.01.
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- Date Issued: 2003
Electrochemical behaviour of thiol-derivatised zinc (II) phthalocyanine complexes and their self-immobilised films at gold electrodes
- Authors: Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290295 , vital:56737 , xlink:href="https://doi.org/10.1016/j.microc.2003.08.002"
- Description: Electrochemical properties of novel, peripherally substituted zinc phthalocyanine complex, octa(4-methylphenylthio-) phthalocyaninatozinc(II) [ZnPc(SC6H4CH3)8] (1a) in DMF solution are presented. This complex showed five quasi-reversible/reversible, diffusion-controlled redox couples. Solution voltammetry of 1a showed little contrast with that of its alkythiol-derivative, octabutylthiophthalocyaninatozinc(II) [ZnPc(SC4H9)8] (1b) in that both thiol-substituents tend to show electron-withdrawing influence on the phthalocyanine ligands; complex 1a showing easier reduction and more difficult to oxidation when compared to 1b and other alkyl derivatives. The voltammetric features of the solid ultrathin films of 1a and 1b, immobilized on gold electrodes via the self-assembling technique, are also presented. Interestingly, the self-assembled films are stable and reproducible and provide good suppression to the following Faradaic processes; gold surface oxidation, solution ion species and underpotential deposition (UPD) of copper.
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- Date Issued: 2003
Ethics beyond the code of conduct - understanding the ethical dilemmas of entrepreneurs
- Authors: Robinson, D A , Van der Mescht, Hennie , Lancaster, Jonathan C S
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: Article
- Identifier: vital:6072 , http://hdl.handle.net/10962/d1001646 , ISSN 1022-2529
- Description: Entrepreneurs choose a particular way of life with the dual aim of maximising profit and gaining a sense of self-satisfaction. In these endeavours, entrepreneurs typically live with the threat of competition and the risk of business failure, while attempting to do their best within the limitations of their resources. This qualitative study first examines existing theories of ethics and ways of applying business ethics and thereafter investigates entrepreneurs' actual experiences by means of in-depth interviews and the use of phenomenology. It finds that entrepreneurs are not guided by any specific code of conduct, and must decide for themselves what is right. It describes the entrepreneurial business ethic, some of the types of dilemmas that they experience and the methods that they have developed to deal with the dilemmas.
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- Date Issued: 2003
Fuelwood availability and use in the Richtersveld National Park, South Africa
- Authors: Shackleton, Charlie M , Guthrie, G , Keirungi, Juliana , Stewart, J
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181461 , vital:43736 , xlink:href=" https://doi.org/10.4102/koedoe.v46i2.66"
- Description: Concern has been voiced about the possible over-use of fuelwood from the riparian fringe by pastoralist herders in the Richtersveld National Park (RNP). This coincided with the current examination and modelling of the supply and use of ecosystem goods and services in the Gariep Basin as part of the Southern African Millennium Assessment (SAfMA). This paper reports on a study to index the current availability of deadwood within the riparian zone of RNP, its relationship with proximity to human habitation, and species preferences of the local herders. Deadwood availability was assessed per woody species and on the ground in 12 transects within the riparian fringe. Herders were interviewed regarding their species preferences, and the composition of woodpiles was examined. There was no relationship between the percentage of attached deadwood on the tree, or the percentage deadwood ground cover, and the distance from herder stockposts. Euclea pseudobenus and Tamarix usneoides were the dominant species in the riparian fringe. There was strong selection for Ziziphus mucronata as a fuelwood species and only marginal or random selection for E. pseudobenus. Tamarix usneoides and Prosopis sp. were abundant in the riparian zone, but were not used for fuelwood. There was a significant difference between species with respect to the mean proportion of the stem that was dead, the highest being Z. mucronata (± 28 % deadwood), followed by T. usneoides (± 12 %). Most of the Prosopis trees had no deadwood. Across all species, the mean percentage dead per tree was approximately 15 %. Additionally, detached deadwood covered just less than 9 % of ground area, averaged across all plots and transects. All the variables measured indicated that there seems to be little need for concern over the current fuelwood extraction activities of pastoralists within the RNP. There was no clear evidence of cutting of branches or deadwood. The abundance of both attached and detached deadwood was not depleted close to human habitation. There was still abundant deadwood, even on preferred species. The most preferred species (Ziziphus mucronata) had the greatest mean proportion of deadwood. The herders stated that they only used deadwood, and that there was plenty. They rarely used driftwood washed down the river, although there was an abundance of it. Thus, overall, there was no sign of depletion of the deadwood resource, even on favoured species, or degradation of the productive capacity for deadwood.
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- Date Issued: 2003
Host-preference and density of woodrose-forming mistletoes (Loranthaceae) on savanna vegetation, South Africa
- Authors: Dzerefos, Cathy M , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181487 , vital:43738 , xlink:href="https://doi.org/10.1023/A:1023991514968"
- Description: In the Bushbuckridge region of South Africa host preference and density of two woodrose-forming mistletoes, Erianthemum dregei (Eckl. and Zeyh.) V. Tieghem and Pedistylis galpinii (Schinz ex Sprague) was quantified in relation to land-use (harvested or unharvested), rainfall (high, more than 660 or low , less than 660 mm year−1) and catenal position (top or lower slope). These two mistletoes are generalist hemi-parasites of savanna trees and shrubs occurring on 25 and 17 hosts respectively, seven of which are shared. Thirty-six percent of woody plant species recorded were found to be hosts. Although Sclerocarya birrea (A. Rich.) Hochst. comprised only 4% of woody plant density in the environment, it was the principal host for both mistletoes, accounting for 71% of total E. dregei and 42% of P. galpinii infection. Mistletoe infection relative to density of Ficus stuhlmanii, Trichilia emetica and Cassine transvaalensis indicated that these were preferential hosts to S. birrea. Mistletoe host preference was negatively correlated with host wood density. Mistletoe number per tree had a weak relationship to canopy size. Mistletoes of all size classes were denser at high rainfall relative to low rainfall sites. Interestingly, the overall mistletoe size class distribution was similar between harvested and unharvested sites. The ratio of living to dead mistletoe was 2 to 1 for E. dregei and 1.5 to 1 for P. galpinii. There are sufficient dead mistletoes in unharvested and harvested areas to satisfy present market demand. Living E. dregei predominated in harvested rather than unharvested areas suggesting that current-harvesting levels had little or no negative effect on the population. In contrast, P. galpinii was denser in unharvested areas possibly owing to its higher market value and thus higher harvesting levels.
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- Date Issued: 2003
If you think that multi-media is not for Africa
- Authors: Garman, Brian
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/454723 , vital:75370 , https://hdl.handle.net/10520/EJC146246
- Description: Over 20 years ago I sat myself down in front of the first Apple Mac to arrive in our department and far from being excited by it, I can remember thinking "this'll never catch on..."
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- Date Issued: 2003
Implementing Location Services in the Location-Transparent, Distributed Environment of the Internet
- Authors: Clayton, Peter G , Preston, Michael , Wells, George C
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430467 , vital:72693 , https://link.springer.com/book/10.1007/b13582?page=1#toc
- Description: This volume contains the papers presented at the 5th International Workshop on Advanced Parallel Processing Technologies, APPT 2003. This series of workshops is designed to strengthen the cooperation between the German and Chinese institutions active in the area of these technologies. It has continued to grow, providing an excellent forum for reporting advances in parallel processing technologies. The 5th workshop itself addressed the entire gamut of related topics, ranging from the architectural aspects of parallel computer hardware and system software to the applied technologies for novel applica-tions. For this workshop, we received over 191 full submissions from researchers all over the world. All the papers were peer-reviewed in depth and qualitatively graded on their relevance, originality, signi?cance, presentation, and the overall appropriateness for their acceptance. Any concerns raised were discussed in the program com-mittee. The organizing committee did an excellent job in selecting 78 papers (Among them, 21 were short ones) for presentation. In short, the papers included here represent the forefront of research from China, Germany, and the other countries.
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- Date Issued: 2003
Indomethacin reduces lipid peroxidation in rat brain homogenate by binding Fe2+
- Authors: Anoopkumar-Dukie, Shailendra , Lack, Barbara , McPhail, Kerry L , Nyokong, Tebello , Lambat, Zaynab , Maharaj, Deepat , Daya, Santy
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304763 , vital:58487 , xlink:href="https://doi.org/10.1023/A:1021958016928"
- Description: One of the hallmarks of Alzheimer's disease (AD) is the progressive degeneration of cholinergic neurons in the cerebral cortex and hippocampus. It is generally accepted that this neuronal degeneration is due to free-radical-induced damage. These free radicals attack vital structural components of the neurons. This implies that agents that reduce free radical generation could potentially delay the progression of AD. Free radical generation in the brain is assisted by the presence of iron, required by the Fenton reaction. Thus, agents that reduce iron availability for this reaction could potentially reduce free radical formation. Since non steroidal anti-inflammatory drugs (NSAIDS) have been shown to reduce the severity of AD, we investigated the possible mechanism by which indomethacin could afford neuroprotection. Our results show that indomethacin (1 mM) is able to reduce the iron-induced rise in lipid peroxidation in rat brain homogenates. In addition, our NMR data indicate that indomethacin binds the Fe2+/Fe3+ ion. This was confirmed by a study using UV/Vis spectrophotometry. The results imply that indomethacin provides a neuroprotective effect by binding to iron and thus making it unavailable for free radical production.
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- Date Issued: 2003
Influence of cyclodextrins on the fluorescence, photostability and singlet oxygen quantum yields of zinc phthalocyanine and naphthalocyanine complexes
- Authors: Tau, Prudence , Ogunsipe, Abimbola O , Maree, Suzanne , Maree, M David , Nyokong, Tebello
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304775 , vital:58488 , xlink:href="https://doi.org/10.1142/S1088424603000562"
- Description: The effects of formation of cyclodextrin inclusion complexes on the photochemical and photophysical properties of zinc phthalocyanine (ZnPc) and various peripherally substituted zinc phthalocyanines as well as zinc naphthalocyanine (ZnNPc) are investigated. The cyclodextrins employed were the hydroxypropyl-γ-cyclodextrin and unsubstituted β-cyclodextrin. Job's plots were employed to confirm the stoichiometry of the inclusion complexes and showed 2:1 and 4:1 (cyclodextrin:phthalocyanine) inclusion behavior. The phthalocyanine inclusion complexes showed larger singlet oxygen quantum yield (ϕΔ) values when compared to the free phthalocyanines before inclusion, for complexes 1 (zinc naphthalocyanine), 2 (zinc tetranitrophthalocyanine) and 4 (zinc tetra-tert-butylphenoxyphthalocyanine). The fluorescence quantum yields generally remained unchanged following inclusion.
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- Date Issued: 2003
Insect Pest Management and Ecological Research, G.H. Walter: book review
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451735 , vital:75073 , https://hdl.handle.net/10520/EJC32546
- Description: This book is a 275-page argument for the place of theoretical biology in pest management research. Its general message is that contemporary pest management research emphasizes application of technology or strategic research at the expense of application of knowledge or tactical research, and that even the application of knowledge should actually be subservient to the development and extension of knowledge, theoretical research. Whenever we study a pest, we are presented with an opportunity to enhance, rather than merely apply, knowledge. It is argued that pest management research is currently failing itself because it is not doing this, and several areas of theoretical biology are identified as offering ways out of this situation.
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- Date Issued: 2003