bluuebunny/crossref_metadata_2025 huggingface dataset:
Kwantumberekening
Authors: Heidema J. , Potgieter P. H. , Fouch´ e W. L.
Published: August 2012

Daar is geen gebrek aan dekking in die laaste paar jaar in wetenskaplike joernale van die onderwerp van kwantumberekening nie. Tereg ook, want dit is ’n nuwe idee met—tot sover—minstens ´ e´ en baie belangrike praktiese toepassing (ontbinding in priemfaktore) sodra die tegnologie redelik omvattende berekenings kan hanteer. Die belangstelling in kwantumverwerking is aangevuur deur beide die besef dat die toenemende miniaturisering noodwendig rekenaarwetenskaplikes met kwantumverskynsels sal konfronteer, en deur die begryp van die potensiaal van massief parallelle verwerking deur die gebruik maak van die Hilbert-ruimtevoorstelling van kwantumstelsels en die spesiale eienskappe van kwantumverstrengeling. Die onderwerp lˆ e by die sameloop van ﬁsika, rekenaarwetenskap en wiskunde en hierdie bydrae verken die idees van di´ e drie gebiede wat die belangrikste rol in kwantumberekening speel en besin oor die deﬁnisies van en die waarskynlike gebruik vir kwantumverwerking asook sy verhouding tot die klassieke berekeningskompleksiteit. Ten slotte word ’n uitgebreide geannoteerde bibliograﬁe verskaf as gids vir die ge¨ ınteresseerde leser tot die literatuur in di´ e onderwerp.AbstractQuantum computing There has been no lack of coverage in the past few years in scientiﬁc journals of the topic of quantum computation. Rightly so, as this is a novel idea with—so far—at least one very important practical application (prime factorisation) as soon as the technology can accommodate reasonably sized computations. Interest in quantum computing has been sparked by both the realization that increasing miniaturisation will eventually bring computer scientists face-to-face with quantum effects, and by the grasping of the potential for massive parallelism inherent in the Hilbert space representation of quantum systems and in the special effects of quantum entanglement. The topic lies at the conﬂuence of physics, computer science and mathematics and this contribution reviews the ideas from these three ﬁelds that play the most important role in quantum computation and reﬂects on the deﬁnitions of and prospective use for quantum computing as well as its relation to classical computational complexity. Finally, an extended annotated bibliography is provided as a guide for the interested reader to the literature in the subject.
’n Ondersoek na fasette van leerders in ’n privaat skool se studieoriëntasie en die verband daarvan met wiskunde- prestasie
Authors: Maree J. G. , Crafford G.
Published: August 2012

Ontoereikende prestasie in wiskunde is ’n enorme probleem in postapartheid Suid-Afrika. In die onderhawige artikel word hierdie verskynsel bespreek en word etlike moontlike redes hiervoor aangedui. Die primêre doel van hierdie studie is onder meer die verkenning van die verband tussen leerders in ’n Suid-Afrikaanse privaat skool se wiskundeprestasie en hul studieoriëntasie. Die Studieoriëntasievraelys in Wiskunde (SOW) is vir die doel van die studie as meetinstrument gebruik. Daar is bevind dat die proporsie leerders met beter studiegewoontes hoër is by vroulike leerders as by manlike leerders. Dit wil voorkom of wiskundeangs, probleemoplossingsgedrag, asook studieomgewing betekenisvolle voorspellers van leerderprestasie in die betrokke privaatskoolkonteks is. Laastens blyk dit dat wiskundeprestasie toeneem met ’n afname in wiskundeangs, maar dat hierdie toename nielineêr is en afplat namate wiskundeangs afneem.AbstractAn investigation into facets of study orientation of learners in a private school and its link with achievement in mathematics Inadequate achievement in mathematics appears to be a major problem in post-apartheid South Africa. In the current article this phenomenon is discussed and possible reasons are indicated. The primary aim of the article is an investigation into the relationship between achievement in mathematics of learners in a South African private school and their study orientation. For this purpose the Study Orientation Questionnaire in Mathematics (SOM) was used as a measuring instrument. It was found that the proportion of learners with more adequate study habits is higher in the case of female learners than in the case of male learners. Mathematics anxiety, problem-solving behaviour and study environment appear to be significant predictors of learner achievement in the private school context corncerned. Lastly, it seems as if mathematics achievement increases with a decrease in mathematics anxiety. However, this decrease is not linear and tapers off with a decrease in mathematics anxiety.
Curculionids in the diet of the white-quilled korhaan: more than just food?
Authors: Kok O. B. , Louw S.v.d. M. , Kok A. C.
Published: August 2012

Analyses of 326 white-quilled korhaan (Eupodotis afraoides) stomach contents collected in the Free State and Northern Cape over a period of 20 years (1984-2004) showed this species to be a mixed feeder concentrating mainly on insects. Based on dry mass prey items of the Isoptera and Coleoptera form the bulk of the diet. According to frequency of occurrence coleopterans, more specifically members of the family Curculionidae, are utilised most often. Indications are that the curculionids, owing to their size and relative hardness of the exoskeleton, fulfil an accessory function with regard to the physical breakdown of coarse food items in the muscular stomach.
Problem-based approach to mathematics in grades 9 and 11 in the Limpopo Province
Authors: Maree J. G. , Molepo J. M. , Owen J. H. , Ehlers R.
Published: August 2012

Teachers of schools in the central region of the Limpopo Province of South Africa received training in a problem-based approach to the teaching and learning of mathematics and introduced these principles into their classes.  Follow-up visits to schools took place on a monthly basis for one year. 800 learners in Grades 9 and 11 completed the Study Orientation Questionnaire in Mathematics (SOM). Mean age in Grade 11 was 17.5 yr. (SD = 1.4), and in Grade 9, 15.1 yr., (SD = 1.2). The differences between the post- and pre-test marks for the two groups were compared. The means for marks in mathematics were significantly different for the two groups.
The use of parallel plate rheology to determine the intrinsic viscosity of polyethylene terephthalate
Authors: Vorster O. C.
Published: August 2012

Determining the intrinsic viscosity of polyethylene terephthalate is complicated by the fact that there are only two methods available at present. The first method is based on solution viscosity. The toxicity of the solvent, as well as the time it takes to carry out an analysis, results in this method not being very practical for everyday use. The second method is limited in its application due to the complexity and availability of the equipment in South Africa. In the present study an alternative method, based on parallel plate rheology, is presented. This method overcomes the problems mentioned and results obtained with it are compared with results obtained with the methods in use at present.
Bakteriële lipopolisakkariede as elisitore van plant verdedigingsresponse
Authors: Office Elna
Published: August 2012

Geen Abstrak.
Stress response of the autonomic nervous system on skydiving and freefall
Authors: Grant C.C. , Claassen N. , Viljoen M.
Published: August 2012

This study investigated the influence of skydiving and freefall, as well as that of visualisation, on the autonomic nervous system balance. The results showed a shift towards sympathetic dominance in the autonomic nervous system balance during skydiving and freefall. This shift was statistically significant in the inexperienced, but not in the experienced skydivers. A similar autonomic stress response was seen in the laboratory during visualisation of skydiving. Further studies are necessary to ascertain whether a difference exists between the extent to which experienced and inexperienced skydivers can induce the biological stress response through visualisation.
Oorkoming van alternatiewe konsepsies aangaande interferensie en diffraksie van lig
Authors: Coetzee A.
Published: August 2012

Geen Abstrak.
Surgery in the Graeco-Roman era
Authors: Retief François P. , Cilliers Louise
Published: August 2012

In the Graeco-Roman era medical treatment characteristically consisted of regimen (diet and a healthy lifestyle), medicaments and surgery – the latter being reserved for those cases in which regimen and medicaments had failed. Evidence of primitive surgery dates back to the Bronze Age, and the Homeric epics describe surgical treatment of war wounds with frequent intervention of the gods. With the arrival of empiric medicine in the 5th century BC, surgery featured prominently in the Hippocratic Corpus by way of excellent contributions on head and orthopaedic surgery in particular. Alexandrian medicine (late 4th century) facilitated surgical development through the knowledge of anatomy and physiology gained from human dissection. Greek medicine brought a much improved standard of surgery to the Roman era (2nd century BC). Physicians were still expected to be proficient in all three modalities of medical practice (above), but surgery was now held in higher regard and specialisation in fields such as eye diseases, obstetrics and women’s diseases, bladder ailments, mouth and throat surgery developed. Military medicine, well organised in Roman times, brought experience in trauma surgery, and procedures penetrating the abdomen and thoracic cavities were no longer uniformly fatal. Veterinary surgery came into being. The first significant surgical textbook after the Hippocratic Corpus was compiled by Celsus in the 1st century AD. From the 3rd century onwards surgery stagnated and the scientific language gradually changed from Greek to Latin. The surgical expertise of the era was carried into the Middle Ages and later predominantly by Islamic physicians.
The mathematical basis of business logistics as a field of study
Authors: Pienaar William J.
Published: August 2012

This article describes the meaning of the word logistics, outlines its mathematical basis and explains the meaning thereof as a contemporary field of study. The concept of logistics management is described in a business context and the strategic, tactical and operational tiers thereof are identified. The relationship that exists between systems analysis and logistics management is indicated. The role and essence of operations research in logistics decision- making are described. The most pertinent operations research topics in the field of logistics as well as the mathematical competencies a logistician should possess, are identified.
The concept of bioavailability and establishing uniform standards for permissible chemical contamination of soil
Authors: Reinecke A. J. , Reinecke S. A.
Published: August 2012

Soils are very heterogeneous substrates providing an environmental matrix with varying spatial and temporal gradients of pH, organic carbon, particle size distribution, moisture content as well as biological factors associated with soil organisms. These chemical, physical as well as biological factors determine the bioavailability of chemicals to soil-dwelling invertebrates. This review of recent literature on the use of the bioavailability concept in soil ecotoxicology indicates that the concept is often used unqualified and indiscriminately to mean different things to different authors. A clear understanding of the concept is crucial for toxicity testing, environmental monitoring, risk assessment and the setting of soil quality criteria since knowledge of the actual exposure of organisms, and not merely the total amount of the chemical, is required. The aim of this paper is to contribute towards a clarification of the concept. Apart from defining or describing bioavailability, the problems related to the comparability of toxicity data between soils and species, inter-soil and inter-species comparisons of toxicity data are discussed. The potential role that biomarkers can play in assessing bioavailability, is touched upon. In an effort to prescribe uniform criteria or standards for environmental quality, both biotic and abiotic characteristics, which determine the bioavailablity of contaminants should be considered. This requires a dynamic approach which takes both uptake processes as well as a variety of other biological factors into consideration. It is concluded that bioavialiblity should be interpreted qualitatively and that the rate of uptake of a contaminant could possibly serve as a measure of bioavailability. The development of standardised protocols for exposure of selected species and the measurement of biological responses with the aid of biomarkers could serve to refine and take risk assessment a step further.
The use of effect size indices to determine practical significance
Authors: Styn H. S. , Ellis S. M.
Published: August 2012

The determination of significance of differences in means and of relationships between variables is of importance in many empirical studies. Usually only statistical significance is reported, which does not necessarily indicate an important (practically significant) difference or relationship. With studies based on probability samples, effect size indices should be reported in addition to statistical significance tests in order to comment on practical significance. Where complete populations or convenience samples are worked with, the determination of statistical significance is strictly speaking no longer relevant, while the effect size indices can be used as a basis to judge significance. In this article attention is paid to the use of effect size indices in order to establish practical significance. It is also shown how these indices are utilized in a few fields of statistical application and how it receives attention in statistical literature and computer packages. The use of effect sizes is illustrated by a few examples from the research literature.
An analytical method to determine phoneme recognition abilities of South African cochlear implant users
Authors: Pretorius L.L. , Hanekom J.J. , Van Wieringen A. , Wouters J.
Published: August 2012

This article describes analytical tests developed to investigate the extent to which Afrikaans- and Englishspeaking South African cochlear implant users recognize phonemes. Vowel stimuli (in a /pVOWELt/ context) and consonant stimuli (in an /aCONSONANTa/ context), uttered by male and female speakers, were recorded and acoustically analysed. Vowel and consonant recognition abilities of respectively nine and eleven local cochlear implant users were subsequently investigated. Typical confusions experienced by cochlear implant users were determined and explained in terms of the acoustic properties of the stimuli. General observations are that implant users find vowels that are identified by spectral characteristics difficult to recognise, while the recognition of temporal properties is better. During consonant recognition, place of articulation is particularly difficult to identify. Results support observations from similar studies conducted for other language groups. These analytical tests may be valuable for creating individualised speech processor settings and monitoring new implant users’ progress in speech recognition ability.
Die Suid-Afrikaanse uitgebreide maritieme gebied: ’n Alternatiewe metode vir die bepaling van die voet van die kontinentale helling
Authors: Pantland N.A. , Van Vuuren J.H.
Published: August 2012

Kuslande het ’n eenmalige geleentheid om by die Verenigde Nasies (VN) aansoek te doen om ’n uitgebreide maritieme gebied, indien hul wetenskaplik kan toon dat die voet van die kontinentale helling (VKH) buite hul soewereine 200 seemyl eksklusiewe ekonomiese sone gele¨e is. Die VN definieer geomorfologies die VKH as die kromme van maksimale buiging tussen die afplattende kontinentale helling en die bodem van die diepsee. In hierdie artikel word daar getoon hoe gediskretiseerde tegnieke uit differensiaalmeetkunde suksesvol gebruik kan word om die VKH benaderd uit satelliet seebodem dieptedata te bepaal, sonder om van data gladstrykingstegnieke gebruik te maak. Hierdie differensiaalmeetkundige benadering is ’n alternatief tot ’n huidige, wyd-gebruikte tegniek vir die bepaling van die VKH en toon dat internasionale spekulasie oor die opportunisme van hierdie tegniek bloot vanuit ’n geomorfologiese perspektief geregverdig mag wees. Die numeriese resultate wat verkry word, is ’n wetenskaplik verantwoordbare aanwyser ten opsigte van die moontlike ligging van die VKH rondom die Suid-Afrikaanse kus.
The florigen mystery
Authors: Groenewald E.G. , Van Der Westhuizen A.J.
Published: August 2012

In order to obtain flowering, different applications of chemicals on plants were tested by several researchers. Substances that were tested were, amongst others, auxin, gibberellin, cytokinin, abscisic acid, prostaglandin; melatonin. All had an effect on flowering. With the aid of molecular-genetic research it was established that the product of certain genes, namely CONSTANS (CO) and FLOWERING LOCUS T (FT) could be the flowering stimulus. It could be a peptide or mRNA.
Medications and their use in the Graeco-Roman era
Authors: Retief François , Cilliers Louise
Published: August 2012

As from the 6th century BC Graeco-Roman medical therapy comprised three components, viz. diet and healthy lifestyle (regimen), surgery and medicaments (pharmacotherapy), of which the latter was the oldest. Although the Corpus Hippocraticum (5th century BC), with minor Egyptian influence, contained no text of medicines as such, and seemed to prefer regimen to medicaments, it nevertheless laid the foundation for the empirical use of pharmacotherapy (free of superstition and magic) for the next millennium. The first Greek herbal was produced by Diocles in the 4th century BC, when the botanist Theophrastus also wrote his classic works on plants which contained a significant contribution on herbal medicines. The Alexandrian Medical School systematized and expanded Hippocratic medicine, and Herophilus introduced compound preparations. The concept that medicaments cure illness by restoring the bodily balance of humours and primary properties was largely perpetuated, but new views on physiology were gradually emerging. Unfortunately the bulk of original contributions from Hellenistic doctors are lost to posterity and only known to us through the writings of for example Celsus and Galen in Roman times. The interesting history of theriac, the so-called universal antidote, is reviewed. In the 1st century Dioscorides produced his Materia Medica which remained an authoritative pharmacopoeia up to modern times. Galen’s empiric views on pharmacotherapy (2nd century), still largely based on Hippocrates, became dogma in Medieval times, but mysticism and superstition gradually swept back into medicine. Retrospectively it is clear that with the exception of certain analgesics and narcotics like opium, Graeco-Roman medicaments were pharmacologically inert (even toxic) and obtained positive results largely through a placebo effect.
Standard residential flood damage functions for South African conditions
Authors: De Villiers Gawie , Viljoen Giel , Booysen Herman
Published: August 2012

Disaster risk management is an integral part of a scientific approach to disaster management. It refers to integrated, multi-sectoral, multi-disciplinary, organizational and operational planning processes and skills to mitigate disasters. Application of the approach necessitates disaster risk analysis, requiring flood damage functions in the case of floods. A flood damage function can be described mathematically, tabularly or graphically and refers to the relationship between flood characteristics like depth and/or speed of floodwater and flood damage to a specific land use type. Research conducted at the University of the Free State indicated the value of standard residential flood damage functions and the necessity for periodic updating to secure contemporary relevance. This article focuses on updating of the latter. The article starts with an introduction to put the development, use and maintenance of standard residential flood damage functions in context with regard to the latest views on disaster risk management, risk assessment, disaster management legislation in South Africa and a computer model TEWA, in which the flood damage functions are used. Aspects that can affect flood damage are briefly discussed, followed by sections on the development and upgrading of structural flood damage functions for formal housing as well as functions for determining damage to housing contents. The development of residential flood damage functions that can be applied nationally forms the main part of the paper and is followed by a brief summary statement.
Do South African and Dutch biology students have different views on nature?
Authors: Eijsackers Herman
Published: August 2012

Lecturing on nature conservancy at Amsterdam and Stellenbosch offered the possibility to investigate if biology students in different countries and cultures have different views on nature and nature conservation. The results of a short questionnaire show a similar broad attitude towards nature and nature conservation in both university student groups. They all want action with respect to global problems (global warming/climate change). But next to that there are also typical national problems like Dutch fisheries discussions and South African eradication of alien species and more attention for water and soil pollution. Moreover, there was a shared interest in more social aspects of nature conservation (education, awareness/consciousness, population growth). A major bias is that the answers express the views of well educated, white people. Extension to young people of other cultural background is needed. So feel free to ask for the questionnaire.
Rock Pigeon x Feral Pigeon hybrid?
Authors: Le Roux Pieter , Kok Ordino , Butler Hennie
Published: August 2012

No Abstract
Factors influencing the choice of profession of first-year teaching students
Authors: Hislop-Esterhuizen N. , Maree J. G. , Van der Linde M. J. , Swanepoel A.
Published: August 2012

The lack of appropriately qualified teachers in South Africa is growing rapidly and debates about the decline in teacher numbers in South Africa are increasing. In this study, the results of an investigation into possible factors that impact on the career choice of teaching students are reported. The reasons why first-year teaching students at the University of Pretoria chose teachings a career were studied by using a non-experimental design (survey design; administering anon-standardised questionnaire). The results revealed, inter alia, that a number of factors influence the career choice of first-year teaching students. Trends that emerged from the current study include the following: many more women than men enter the teaching profession; relatively few African language speaking students choose education as a field of study and the role of parents in helping their children to choose a career cannot be underestimated.
The influence of health education on the prevalence of schist some infected learners in aschistosome endemic area in the Limpopo Province
Authors: Wolmarans Corrie , De Kock Kenné
Published: August 2012

During this study selected direct and indirect educational methods were evaluated as a means of decreasing the prevalence of schist some infections in school children living in a schistosomeendemic area. Two direct (puppet show and flip chart) and three indirect (notice board, poster and education via parents or guardians) educational methods were evaluated. Schist some infected learners were identified by means of parasitological methods, their knowledge concerningschistosomiasis was tested in a questionnaire and information regarding water and sanitation facilities at their disposal was collected. Local health authorities facilitated treatment for this disease, while local teachers were involved in conveying the various educational programmes. Anoticeable increase in the learner’s knowledge regarding schistosomiasis was evident after only two educational opportunities, while a significant decrease in the cumulative prevalence of infection was recorded during the investigation among all the groups receiving education. Statistical analyses revealed that the puppet show, flipchart and poster were the most effective methods used to lower the prevalence of infection, while involving parents or guardians in the process proved to be the least effective method employed during the study.
A philosophical basis for the holistic study of landscape development in Geomorphology
Authors: Barker Charles , De Villiers Gawie
Published: August 2012

The development of Geomorphology from two former major disciplines (Geography and Geology),makes it difficult for practitioners to accept a single major meta-paradigm as is the case with other earth sciences. It is also clear from current developments in the discipline, that the move away from the traditional qualitative research in micro-scale environments left a methodological gap in investigations into larger (meso-scale) phenomena. In this article, paradigms and science are examined with special reference to Geography as one of the parental sciences of Geomorphology (a view which is largely held in South Africa). After an elucidation of a meta-paradigm for Geomorphology, this meta-paradigm is then discussed in greater detail. Critical issues such as time and space and the way in which they are treated in Geomorphology are considered. Five social paradigms (functionalism, positivism, pragmatism, realism and the general systems theory or holism) used in Geomorphology are explained in as far as they have been applied to the discipline in the past. These are then linked to philosophical concepts and research approaches in landscape development in particular. The historical evolution of landscape development studies and principles of landscape development such as quantitative methods, antagonism, stability, equilibrium, catena’s, directedness, tectonics, and environmental variables provide the foundation from which the authors formulate a philosophical basis, “systemic realism”, for the integration of process and historic-genetic studies in Geomorphology. Several criteria are given for testing the proposed methodology, based on the components from which the approach was formulated. Results from a case study done on the Modder River catchment in the central Free State are compared with the suggested approach. Firstly, a conceptual model of the catchment is discussed. The identification of possible causal processes and environmental conditions is made from the conceptual model, previous studies and the spatial distribution of land forms and geological features in the catchment. Finally, some light is shed on the possible future development of the landscape. It is the authors’ contention that systemic realism forms a sound basis for future research in landscape development and, from there, provides a guideline to resource management.
’n Universele programmeerbare kwantumrekenaar?
Authors: Potgieter P. H. , Heidema J. , Jones E. G.
Published: August 2012

Refer to pdf for english Abstract
Relationship between group size and feeding success of cattle egrets (Bubulcus ibis) in the central Free State
Authors: Butler Hennie , Kok Ordino
Published: August 2012

Regardless of habitat or time of day, cattle egrets feeding independently of hosts generally occurring larger groups than those feeding in close association with ungulates. The average group size of three individuals feeding in association with hosts stays remarkably constant with regard to divergent situations. Based on the type of habitat and the grazing speed of the host concerned, cattle egrets achieve the highest feeding success (number of prey items) with the least energy inputs (number of paces) in association with cattle, and to a lesser extent with the closely related buffalo. Compared to solitary birds, cattle egrets feeding in groups experience without exceptional higher feeding success. Results of feeding experiments, as well as the exceptional occurrence of so-called feeding lines, confirm the phenomenon that the feeding success of cattle egrets correlates closely with the size of the feeding group.
Chronological review of South African guidelines for residential average annual water demand with property size as independent variable
Authors: Jacobs Heinz
Published: August 2012

Guidelines for residential average annual water demand (AADD) based on property size were introduced to the South African Civil Engineering fraternity in about 1960, with the most recent publication of such guidelines in 2008. The AADD forms the basis of calculations performed during the design and analysis of water systems. Over the years technology has improved, scientific progress was made and demand has changed, resulting in improved and updated guidelines for AADD. Changes in the guidelines over the years could be considered to be a result of improvement– larger and more accurate data sets are nowadays analysed statistically by improved computer technology. Also, the changes are considered to be the result of scientific advances in the fields of metering, modelling and analysis of water demand. Finally, actual changes in demand occur with time. This research provides the first documented review of the chronological development of AADD guidelines in South Africa. It is noted that only two guidelines were used for relatively long periods of time. In both cases the guidelines would not compare favourably to others from a pure research perspective, but their successful application is the result of a co-ordinated educational and marketing effort. The value of a sustained guideline structure (AADD versus stand size in this case) is also underlined.
Projects to improve mathematics performance at a university of technology
Authors: Louw Ina
Published: August 2012

Lecturers at tertiary institutions have been expressing concern about the quality of students in mathematics for a long time now. Blame is usually placed at the door of secondary schools, but through put ﬁgures are still determining state subsidies and as such necessitate institutions to constantly revisit their efforts in terms of improving performance in mathematics. In this article, the results of two studies to improve the mathematics performance at a technical university are reported. The ﬁrst study took place at the former Technikon Northern Gauteng and was an action research project with an experimental design. The study entailed the implementation of tutorial sessions and it revealed certain traits of tertiary mathematics education. Data were collected through structured observation, questionnaires and focus group interviews. A standardized questionnaire, Study Orientation Questionnaire in Maths (SOM), was introduced and “study habits” was the ﬁeld in the test that featured most signiﬁcantly in both the experimental and the control groups. The results revealed, inter alia, that timely assessment is needed to detect and correct misconceptions as soon as possible. It also pointed out that attendance of lectures (and tutorials) impacted strongly on performance. Lastly, it was found that students preferred communicating mathematics through the medium of English and not by using their mother tongue. The second project was conducted at the Tshwane University of Technology (TUT) and consisted of an investigation into assessment practices in ﬁrst year mathematics. The study was executed with action research as strategy and data were collected through interviews, questionnaires and focus group interviews. Qualitative and quantitative data were collected and respondents were exposed to contemporary assessment strategies as suggested by OBE. The aim of the study was to enhance the respondents’ insight into contemporary assessment strategies and to empower them to execute their assessment in a more accountable way. The merger of the institution was still underway at the time, which left many respondents with questions and uncertainties about their future. Some of the ﬁndings were, inter alia, that some respondents were convinced that new assessment strategies would lower the standard of teaching; some respondents mentioned the poor quality of students and were convinced that the Tshwane University of Technology would beneﬁt from reviewing their admission criteria, and respondents cited large class groups, lack of marking assistance and ignorance about Outcomes Based Education (OBE) as reasons for failing to undertake assessment renewal. In the mean time class groups got even bigger and a new solution needs to be found as a matter of urgency
From the Fermat points to the De Villiers3 points of a triangle
Authors: De Villiers Michael
Published: August 2012

The article starts with a problem of ﬁnding a point that minimizes the sum of the distances to the vertices of an acute-angled triangle, a problem originally posed by Fermat in the 1600’s, and apparently ﬁrst solved by the Italian mathematician and scientist Evangelista Torricelli. This point of optimization is therefore usually called the inner Fermat or Fermat-Torricelli point of a triangle. The transformation proof presented in the article was more recently invented in 1929 by the German mathematician J. Hoffman. After reviewing the centroid and medians of a triangle, these are generalized to Ceva’s theorem, which is then used to prove the following generalization of the Fermat-Torricelli point from [3]: “If triangles DBA, ECB and FAC are constructed outwardly (or inwardly) on the sides of any ∆ABC so that ∠DAB =∠CAF , ∠ DBA = ∠ CBE and ∠ ECB = ∠ ACF then DC, EA and FB are concurrent.”However, this generalization is not new, and the earliest proof the author could trace is from 1936 by W. Hoffer in [1], though the presented proof is distinctly different. Of practical relevance is the fact that this Fermat-Torricelli generalization can be used to solve a “weighted” airport problem, for example, when the populations in the three cities are of different size. The author was also contacted via e-mail in July 2008 by Stephen Doro from the College of Physicians and Surgeons, Columbia University, USA, who was considering its possible application in the branching of larger arteries and veins in the human body into smaller and smaller ones. On the basis of an often-observed (but not generally true) duality between circumcentres and in centres, it was conjectured in 1996 [see 4] that the following might be true from a similar result for circumcentres (Kosnita’s theorem), namely: The lines joining the vertices A, B, and C of a given triangle ABC with the incentres of the triangles BCO, CAO, and ABO (O is the incentre of ∆ABC), respectively, are concurrent (in what is now called the inner De Villiers point). Investigation on the dynamic geometry program Sketchpad quickly conﬁ rmed that the conjecture was indeed true. (For an interactive sketch online, see [7]). Using the aforementioned generalization of the Fermat-Torricelli point, it was now also very easy to prove this result. The outer De Villiers point is similarly obtained when the excircles are constructed for a given triangle ABC, in which case the lines joining the vertices A, B, and C of a given triangle ABC with the incentres of the triangles BCI1, CAI2, and ABI3 (Ii are the excentres of ∆ABC), are concurrent. The proof follows similarly from the Fermat-Torricelli generalization.
Chemo-Enzymatic Synthesis of Ester-Linked 2-Phenylindole-3-Carboxaldehyde-Monosaccharide Conjugate as Potential Prodrug
Authors: Shimoda Kei , Hamada Manabu , Yokoi Hiroshi , Hamada Hiroki
Published: August 2012

Chemo-enzymatic synthesis of ester-linked 2-phenylindole-3-carboxaldehyde-glucose conjugate (2-phenylindole-3-carboxyl-10″-O-β-D-glucosyl ester) was achieved by using plant cell cultures as biocatalysts. The anticancer agent, 2-phenylindole-3-carboxaldehyde, induced apoptosis in cells, whereas 2-phenylindole-3-carboxyl-10″-O-β-D-glucosyl ester showed no cytotoxicity and induced no apoptosis.
Genetic Polymorphism of Plasmodium falciparum Merozoite Surface Protein-1 and -2 and Diversity of Drug Resistance Genes in Blood Donors from Bamako, Mali
Authors: Thomas Bolaji N. , Petrella Carlyn R. , Crespo Stephanie R. , Thakur Tanya J. , Moulds Joann M. , Diallo Dapa A.
Published: August 2012

We examined malaria infection in asymptomatic blood donors from Mali, analyzing allelic diversity of Plasmodium falciparum (Pf) merozoite surface proteins (msp) -1 and -2 as well as the distribution of sulphadoxine-pyrimethamine (SP) resistance genes. A total of 140 genomic DNA samples were screened. Allele-specific nested polymerase chain reaction (PCR) analysis of Pfmsp-1 and Pfmsp-2 was performed, plus fragment analysis of the polymorphic regions to identify allelic diversity of the parasite population. We found parasite positivity due to Pf alone in 20.7% of these donors. Diverse allelic polymorphism of Pfmsp-1 and Pfmsp-2 was identified, with a high rate of multiplicity of infection (1.84 and 1.82 for Pfmsp-1 and Pfmsp-2, respectively). In addition, we found a high degree of SP resistance, with mutations at several dhfr and dhps codons. We conclude that there is an extensive diversity of Pfmsp-1 and Pfmsp-2 allelic types and SP drug resistance in Pf-infected donors from Mali.
Through Which Channels Can Remittances Spur Economic Growth in MENA Countries?
Authors: Ben Mim Sami , Ben Ali Mohamed Sami
Published: August 2012

This paper studies the remittances’ effect on economic growth. Using panel data techniques, the authors estimate several specifications to provide support of such relationship for MENA countries over the period 1980–2009. The findings provide new robust evidence on how remittances are used in MENA countries and detect the main channels which may interfere in this process. Estimation outcomes show that the most important part of remittances is consumed and that remittances stimulate growth only when they are invested. Moreover, empirical results suggest that remittances can enhance growth by encouraging human capital accumulation. Human capital is therefore an effective channel through which remittances stimulate growth in MENA countries.
Impact of very short-lived halogens on stratospheric ozone abundance and UV radiation in a geo-engineered atmosphere
Authors: Tilmes S. , Kinnison D. E. , Garcia R. R. , Salawitch R. , Canty T. , Lee-Taylor J. , Madronich S. , Chance K.
Published: August 2012

Abstract. The impact of very short-lived (VSL) halogenated source species on the ozone layer and surface erythemal ultraviolet radiation (UVERY) is investigated in the context of geo-engineering of climate by stratospheric sulfur injection. For a projected 2040 model atmosphere, consideration of VSL halogens at their upper limit results in lower ozone columns and higher UVERY due to geo-engineering for nearly all seasons and latitudes, with UVERY rising by 12% and 6% in southern and northern high latitudes, respectively. When VSL halogen sources are neglected, future UVERY increases due to declines in ozone column are nearly balanced by reductions of UVERY due to scattering by the higher stratospheric aerosol burden in mid-latitudes. Consideration of VSL sources at their upper limit tips the balance, resulting in annual average increases in UVERY of up to 5% in mid and high latitudes. Therefore, VSL halogens should be considered in models that assess the impact of stratospheric sulfur injections on the ozone layer.
Evaluation of continuous water vapor δD and δ18O measurements by off-axis integrated cavity output spectroscopy
Authors: Kurita N. , Newman B. D. , Araguas-Araguas L. J. , Aggarwal P.
Published: August 2012

Abstract. Recent commercially available laser spectroscopy systems enabled us to continuously and reliably measure the δD and δ18O of atmospheric water vapor. The use of this new technology is becoming popular because of its advantages over the conventional approach based on cold trap collection. These advantages include much higher temporal resolution/continuous monitoring and the ability to make direct measurements of both isotopes in the field. Here, we evaluate the accuracy and precision of the laser based water vapor isotope instrument through a comparison of measurements with those found using the conventional cold trap method. A commercially available water vapor isotope analyzer (WVIA) with the vaporization system of a liquid water standard (Water Vapor Isotope Standard Source, WVISS) from Los Gatos Research (LGR) Inc. was used for this study. We found that the WVIA instrument can provide accurate results if (1) correction is applied for time-dependent isotope drift, (2) normalization to the VSMOW/SLAP scale is implemented, and (3) the water vapor concentration dependence of the isotopic ratio is also corrected. In addition, since the isotopic value of water vapor generated by the WVISS is also dependent on the concentration of water vapor, this effect must be considered to determine the true water vapor concentration effect on the resulting isotope measurement. To test our calibration procedure, continuous water vapor isotope measurements using both a laser instrument and a cold trap system were carried out at the IAEA Isotope Hydrology Laboratory in Vienna from August to December 2011. The calibrated isotopic values measured using the WVIA agree well with those obtained via the cold trap method. The standard deviation of the isotopic difference between both methods is about 1.4‰ for δD and 0.28‰ for δ18O. This precision allowed us to obtain reliable values for d-excess. The day-to-day variation of d-excess measured by WVIA also agrees well with that found using the cold trap method. These results demonstrate that a coupled system, using commercially available WVIA and WVISS instruments can provide continuous and accurate isotope data, with results achieved similar to those obtained using the conventional method, but with drastically improved temporal resolution.
Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements
Authors: Waquet F. , Cornet C. , Deuzé J.-L. , Dubovik O. , Ducos F. , Goloub P. , Herman M. , Lapionak T. , Labonnote L. , Riedi J. , Tanré D. , Thieuleux F. , Vanbauce C.
Published: August 2012

Abstract. Most of the current aerosol retrievals from passive sensors are restricted to cloud-free scenes, which strongly reduces our ability to monitor the aerosol properties at a global scale. The presence of Aerosols Above Clouds (AAC) affects the polarized light reflected by the cloud layer, as shown by the spaceborne measurements provided by the POlarization and Directionality of Earth Reflectances (POLDER) instrument. We present new developments that allow retrieving the properties of mineral dust particles when they are present above clouds. These particles do not much polarize light but strongly attenuate the polarized cloud bow generated by the beneath liquid cloud layer. The spectral attenuation can be used to qualitatively identify the nature of the particles (i.e. mineral dust particles or biomass burning aerosols) whereas the magnitude of the attenuation is related to the optical thickness of the aerosol layer. We provide accurate polarized radiance calculations for AAC scenes and evaluate the contribution of the POLDER polarization measurements for the simultaneous retrieval of the aerosol and clouds properties. We investigate various scenes with mineral dust particles and biomass burning aerosols above clouds. We found that the magnitude of the primary cloud bow cannot be accurately estimated with a plane parallel transfer radiative code. The errors for the modelling of the polarized cloud bow are between 5 and 8% for homogenous cloudy scenes, as shown by a 3-D radiative transfer code. For clouds, our results confirm that the droplets size distribution is narrow in high latitude ocean regions and that the droplets effective radii retrieved from polarization measurements and from total radiance measurements are generally close for AAC scenes (departures smaller than 2 μm). For the aerosols, the POLDER polarization measurements are primarily sensitive to the particles load, size distribution, shape and real refractive index. An algorithm was developed to retrieve the Aerosol Optical Thickness (AOT) and the Angström exponent above clouds in an operational way. This method was applied to various regions of the world and time period. Large mean AOTs above clouds at 0.865 μm (>0.3) are retrieved for oceanic regions near the coasts of South Africa and California (>0.1) that correspond to biomass burning aerosols whereas even larger mean AOTs above clouds for mineral dust particles (>0.6) are also retrieved near the coasts of Senegal (for June–August 2008). For these regions and time period, the direct AAC radiative forcing is likely to be significant. The final aim of this work is the global monitoring of the aerosol above clouds properties and the estimation of the direct aerosol radiative forcing in cloudy scenes.
Geosynchronous magnetic field responses to fast solar wind dynamic pressure enhancements: MHD field model
Authors: Sun T. R. , Wang C. , Borodkova N. L. , Zastenker G. N.
Published: August 2012

Abstract. We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (Pd) enhancements. Taking three Pd enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component Bz can be efficiently predicted by the MHD model. The predicted B and Bz varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., Bx and By). In contrast, the limitations of T01 model in predicting responses to fast Pd enhancements are presented.
Internal respiration of Amazon tree stems greatly exceeds external CO2 efflux
Authors: Angert A. , Muhr J. , Negron Juarez R. , Alegria Muñoz W. , Kraemer G. , Ramirez Santillan J. , Barkan E. , Mazeh S. , Chambers J. Q. , Trumbore S. E.
Published: August 2012

Abstract. Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate, because of emission or removal of CO2 by transport in xylem water. Here we used the ratio between CO2 efflux and O2 influx in stems of tropical forest trees to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. This ratio, which we defined here as apparent respiratory quotient (ARQ), is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. However, using a stem chamber approach to quantifying ARQ we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~35%) is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the tree, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate, for the first time, the existence of a~considerable internal flux of CO2in the stem of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for several percent of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also indicate, in agreement with previous work, that the widely used CO2 efflux approach for determining stem respiration is unreliable. We demonstrate here a field applicable approach for measuring the O2 uptake rate, which we suggest to be a more appropriate method to estimate stem respiration rates.