Vraagstelling vir bemagtiging: die tradisionele klaskamer as vertrekpunt

Questioning for empowerment: the traditional classroom as point of departure. This article focuses on the question as the most salient element in classroom discourse. A theoretical discussion of the question from a linguistic as well as a didactic perspective is followed by a description of the use of questions in some Grade 4 classrooms in Mangaung on the eve of the implementation of Curriculum 2005. Transcriptions of video-recordings of six history lessons (three of which were presented through the medium of Southern Sotho and three through the medium of English) were analysed to determine how teachers use specific types of questions with the intention of achieving certain objectives or outcomes in the social environment of the classroom. Among the findings discussed is how the role of the teacher as sole source of knowledge is reflected in the questioning patterns. The vast majority of questions are not real questions, but examination questions posed by the teacher to ascertain whether learning is taking place. The learners do not ask questions. Although there is evidence of meaning negotiation, only a few learners take part in this process. The others are passive listeners whose responses are limited to chorus answers. Learners can only be empowered if they ask real questions that will lead to the solving of problems. In the new educational dispensation, teachers are faced with the challenge of asking questions that will lead to an inquisitive attitude in the case of learners. The research on questioning in the classroom is ongoing. A later work will report on questioning in changing classrooms where a learning-centred, task-based approach is introduced. South African Journal of Education Vol.23(3) 2003: 212-21

Introduction of co-operative learning to Grade 4 learners in some disadvantaged schools

No Abstract. South African Journal of Education Vol. 23 (2) 2003: pp. 107-11

Global entrainment of transcriptional systems to periodic inputs

This paper addresses the problem of giving conditions for transcriptional systems to be globally entrained to external periodic inputs. By using contraction theory, a powerful tool from dynamical systems theory, it is shown that certain systems driven by external periodic signals have the property that all solutions converge to a fixed limit cycle. General results are proved, and the properties are verified in the specific case of some models of transcriptional systems. The basic mathematical results needed from contraction theory are proved in the paper, making it self-contained

Mixture models for analysis of melting temperature data

BackgroundIn addition to their use in detecting undesired real-time PCR products, melting temperatures are useful for detecting variations in the desired target sequences. Methodological improvements in recent years allow the generation of high-resolution melting-temperature (Tm) data. However, there is currently no convention on how to statistically analyze such high-resolution Tm data.ResultsMixture model analysis was applied to Tm data. Models were selected based on Akaike's information criterion. Mixture model analysis correctly identified categories in Tm data obtained for known plasmid targets. Using simulated data, we investigated the number of observations required for model construction. The precision of the reported mixing proportions from data fitted to a preconstructed model was also evaluated.ConclusionMixture model analysis of Tm data allows the minimum number of different sequences in a set of amplicons and their relative frequencies to be determined. This approach allows Tm data to be analyzed, classified, and compared in an unbiased manner.</p

Carcass characteristics and meat quality of progeny of five Merino dam lines, crossed with Dormer and Suffolk sires

This study details the slaughter traits of lambs born from a terminal crossbreeding experiment that involved five Merino type dam lines crossed with Dormer and Suffolk sires. Dam lines included dual purpose types; South African Mutton Merino (SAMM), Dohne Merino, SAMM rams crossed to commercial Merino ewes (SAMM cross) and specialist Merino lines selected either for clean fleece weight (FW+) or for an increased fertility (Rep+). Data include between 228 and 483 individual records, depending on the trait. The unadjusted fat depth 25 mm from the midline at the 13th rib of lambs from dual-purpose ewes was between 22 and 32% greater than that of lambs from FW+ Merino ewes. Progeny from Rep+ Merino ewes showed a closer resemblance to the progeny of dual-purpose breeds than to those of FW+ Merino ewes in this instance. Adjustment for slaughter weight eliminated these differences. The initial pH of meat from progeny of FW+ Merino ewes was lower than that from progeny of dual-purpose ewes, and Rep+ Merino ewes. No differences in Warner-Bratzler shear values of the meat were found between the different crosses. Crossbred progeny of the Merino lines performed satisfactorily for all the traits considered, and will not be discriminated against in the market. No conclusive differences in favour of either sire breed were found. Keywords: Dohne Merino, meat quality, SA Mutton Merino, terminal crossbreeding South African Journal of Animal Science Vol. 38 (4) 2008: pp. 355-36

Antimycobacterial and cytotoxicity evaluation of the constituents of Monodora carolinae

Phytochemical investigation of the stem bark of the recently described species Monodora carolinae (Annonaceae) afforded prenylindole derivatives (E)-4-(1H-indol-6-yl)-but-3-en-2-one (1), 5-formylindole (2), fatty acid (Z)-hexade-7-enoic acid (3) and the lignanamide cannabisin B (4). The structures of the isolated compounds were established using NMR and MS analyses. The antimycobacterial activities of the extracts and isolated compounds were evaluated against Mycobacterium madagascariense (MM) and M. indicus pranii (MIP) using the two-fold microtitre dilution method. While the extracts exhibited minimum inhibitory concentration (MIC) ranging from 500 – 1000 ìg/mL, the isolated compounds were 125 – 250 ìg/mL, indicating very low activity. Cytotoxic effects were evaluated using brine shrimp larvae whereby the ethanolic extract of the root bark exhibited the lowest LC50 (&lt; 3ìg/mL). Isolation of prenylindole derivatives is ofchemotaxonomic significance that affirms taxonomic placement of this plant species into the genus Monodora. This is the first time cannabisin B is reported from the genus Monodora.Keywords: Monodora carolinae, Annonaceae; prenylindole, cannabisin B, (Z)-hexade-7-enoic acid; antimycobacterial, cytotoxicity

A comparison between the body composition, carcass characteristics and retail cuts of South African Mutton Merino and Dormer sheepe/pj

No Abstract. South African Journal of Animal Science Vol. 34 (1) 2004: pp.44-5

Production of five Merino type lines in a terminal crossbreeding system with Dormer or Suffolk sires

This study details the production performance of ewes and lambs that originated from a terminal crossbreeding experiment that involved five Merino type dam lines and two terminal crossbreeding sire lines from 1999 to 2002. Ewe lines were SA Mutton Merino (SAMM), SAMM rams crossed to Merino ewes (SAMM cross), Dohne Merino, as well as specialist Merino lines selected for clean fleece weight (FW+) and for an increased reproduction rate (Rep+). Dormer and Suffolk rams were used as sire breeds on these ewes. Data include 777 birth and 605 weaning records of lambs and 562 production year records of ewes. At birth the progeny of SAMM ewes were heavier than those of the other ewe lines, while FW+ ewes produced smaller lambs at birth than SAMM cross and Rep+ ewes. Lamb survival was not significantly affected by ewe line or sire breed. The progeny of the dual-purpose ewe lines (SAMM, SAMM cross and Dohne Merino) were heavier than those of Merino ewes (FW+ and Rep+) at weaning. No sire breed difference was found for birth or weaning weight. The joining weights of dual-purpose ewe lines were higher than those of Merinos. Although considerable variation was found between ewe lines in terms of lamb output (number or weight of lamb weaned per ewe joined), the only significant difference was for weight of lamb weaned between SAMM cross and FW+ Merino ewes. Means for weight of lamb weaned per joining (in kg) were 37.3 for SAMM ewes, 39.6 for SAMM cross ewes, 35.5 for Dohne Merino ewes, 28.9 for FW+ ewes and 34.6 for Rep+ ewes. No differences in ewe reproduction were found between ewes joined to Dormer or Suffolk rams. The clean wool production of SAMM ewes amounted to 46% of that recorded in FW+ ewes. Corresponding percentages were 68% for SAMM cross ewes, 74% for Dohne Merino ewes and 90% for Rep+ ewes. The wool of SAMM ewes was slightly coarser in diameter than those of SAMM cross and FW+ ewes, which in turn was coarser than those of Rep+ and Dohne Merino ewes. The economic viability of crossbreeding programs involving the respective ewe lines would depend on the ratio between the prices of wool and lamb. No conclusive advantage could be demonstrated in favour of any of the sire breeds. Keywords: Fibre diameter, Lamb growth, Lamb output, Reproduction, South African sheep breeds, Wool yield South African Journal of Animal Science Vol.33(4) 2003: 223-23

Observer design for a class of nonlinear systems combining dissipativity with interconnection and damping assignment

A nonlinear observer design approach is proposed that exploits and combines port-Hamiltonian systems and dissipativity theory. First, a passivity-based observer design using interconnection and damping assignment for time variant state affine systems is presented by applying output injection to the system such that the observer error dynamics takes a port-Hamiltonian structure. The stability of the observer error system is assured by exploiting its passivity properties. Second, this setup is extended to develop an observer design approach for a class of systems with a time varying state affine forward and a nonlinear feedback contribution. For a class of nonlinear systems, the theory of dissipative observers is adapted and combined with the results for the passivity-based observer design using interconnection and damping assignment. The convergence of the compound observer design is determined by a linear matrix inequality. The performance of both observer approaches is analyzed in simulation examples