3,409 research outputs found
The role of Umkhonto we Sizwe (MK) in the national liberation struggle in South Africa with reference to the rural far northern Transvaal, 1976-1990
No full textIncludes bibliographical references (leaves 250-275)
Experiencing the armed struggle : the Soweto generation and after
No full textIncludes bibliographical references (p. 354-369).This study explores the experiences of the rank-and-file soldiers of Umkhonto we Sizwe and the Azanian People's Liberation Anny. Extensive interviews by the author and other researchers reveal the voices of the soldiers themselves. The African National Congress and Pan African Congress archives at the University of the Western Cape and the University of Fort Hare supplement and verify these oral testimonies, as do some published sources. Most previously published materials about the armed struggle against apartheid have already focused on diplomacy, strategy and tactics, operations, leadership, and human rights abuses to the neglect of the soldiers' actual experiences. This study complements these with significant new oral history materials from the Soweto generation of soldiers and their successors. When dealing with MK, many authors have documented issues of the camp structure in Angola, and operations inside South Africa, so much of this detail is only addressed briefly, leaving space to explore the soldiers' experiences. In the case of APLA, very little has been written on its history, and more detail is provided on these subjects. This study therefore deals with the soldiers' politicisation and motivation for joining the armed struggle, their experiences in leaving South Africa and training in exile, the crises in exile which limited their effectiveness for a time, their return to fight in South Africa, and their difficulties in the "new" South Africa. These materials reveal that vast problems remain facing these veterans of the struggle against apartheid, and that they have the potential, if properly supported and employed, to contribute substantially to the development of present day South Africa. Conversely, if their neglect continues, they also have the potential to bring vast harm to the country. Further use of the investigative tools of oral history, especially if extended to the former soldiers' vernacular languages, is necessary to augment the history of South Africa, and these soldiers' contributions
Effect of brief daily resistance training on rapid force development in painful neck and shoulder muscles: randomized controlled trial
No full textTo determine the effect of small daily amounts of progressive resistance training on rapid force development of painful neck/shoulder muscles.METHODS:198 generally healthy adults with frequent neck/shoulder muscle pain (mean: age 43.1 years, computer use 93% of work time, 88% women, duration of pain 186 day during the previous year) were randomly allocated to 2- or 12 min of daily progressive resistance training with elastic tubing or to a control group receiving weekly information on general health. A blinded assessor took measures at baseline and at 10-week follow-up; participants performed maximal voluntary contractions at a static 90-degree shoulder joint angle. Rapid force development was determined as the rate of torque development and maximal muscle strength was determined as the peak torque.RESULTS:Compared with the control group, rate of torque development increased 31.0 Nm s(-1) [95% confidence interval: (1.33-11.80)] in the 2-min group and 33.2 Nm s(-1) (1.66-12.33) in the 12-min group from baseline to 10-week follow-up, corresponding to an increase of 16.0% and 18.2% for the two groups, respectively. The increase was significantly different compared to controls (P<0.05) for both training groups. Maximal muscle strength increased only ~5-6% [mean and 95% confidence interval for 2- and 12-min groups to control, respectively: 2.5 Nm (0.05-0.73) and 2.2 Nm (0.01-0.70)]. No significant differences between the 2- and 12-min groups were evident. A weak but significant relationship existed between changes in rapid force development and pain (r = 0.27, P<0.01), but not between changes in maximal muscle strength and pain.CONCLUSION:Small daily amounts of progressive resistance training in adults with frequent neck/shoulder pain increases rapid force development and, to a less extent, maximal force capacity
Dawn Aerospace Mk-III Spaceplane Aerothermodynamic Analysis
No full textDawn Aerospace is developing a horizontal take-off and landing two stage to orbit partially-reusable launcher concept. The re-usable first stage spaceplane operates on a return to launch site trajectory and integrates into the existing airspace, flying as an UAV. For any re-entry vehicle the design needs to account for aerothermodynamic behaviour around the vehicle, to ensure the structure can survive the re-entry temperatures. The unique mission of the Mk-III means the thermal design considerations are unique and provide a new engineering challenge and research topic. This thesis investigates the aerothermodynamic behaviour of the Mk-III flow and structure. A loosely coupled model was created for this purpose, which couples engineering methods to predict the aerothermodynamics and the thermal behaviour of the structure. The coupling is done by transferring the external skin temperature and convective heat flux between the two simulations. The primary research question for this thesis is “What thermal protection systems have potential to be implemented on the Dawn Aerospace Mk-III spaceplane for a range of different design trajectories.” Two thermal protection systems (TPS) and material choices have been identified as potential solutions. The first is a fully titanium structure, which can handle the temperature experienced by the Mk-III for all trajectories at every point along the vehicle. The second is a combined titanium and BMI CF structure with an insulation layer on the BMI CF. The titanium is required for the temperatures experienced on the vehicle’s leading edges, while the BMI CF has been identified as suitable in areas away from the leading edge if protected by an insulation TPS. A benefit this option produces is that the insulation layer can be changed in thickness to lighten the vehicle for lower design trajectories, therefore creating different vehicles for different trajectories. However, combining a metal with a composite could pose manufacturing issues such as cost for different manufacturing processes and joining problems. This thesis could not properly trade-off between these two options due to it being outside the scope of this thesis and due to limitations in detailed structural knowledge. These two material choices were chosen from four materials analysed in the thesis and four different TPS. Other TPS were not suitable at decreasing the structural temperature for the Mk-III mission or had an unjustifiable weight penalty. The other material choices would have been suitable in certain situations but were heavier than the current proposed options and might have required a TPS. This thesis provides valuable insight in what suitable material and TPS choices could be for the Mk-III mission. It also shows that for any future material and TPS choice to be made, a comprehensive structural analysis is required. Mass is a key trade-off parameter between the two proposed solutions and a better structural analysis is required for any further trade-off.Aerospace Engineerin
On the determinant of Up on Mk(p,χ)
No full textIn this work, for p a prime, we compute the absolute value of the determinant of the UpUp-operator on the vector space Mk(p,χ)Mk(p,χ) of holomorphic modular forms of weight k and level Γ0(p)Γ0(p) with character χχ. As an implication, we confirm a number of conjectures of the second author
Changing dogma regarding the conformation of electron transferring menaquinone (MK)
No full text2017 Spring.Includes bibliographical references.Menaquinone-9 (MK-9) is the natural substrate containing a naphthoquinone and an isoprenyl side-chain with nine isoprene units that carry out the electron transfer for the Mycobacterium tuberculosis. We present studies aiming to understand the chemical and biochemical properties of hydrophobic MK molecules. Specifically, we are investigating the MK derivative with two isoprene units, MK-2, because it provides us with the base structure containing the naphthoquinone unit and the isoprene side-chain. Its synthesis is relatively simple because the precursors are commercially available, which allows for large scale preparation and detailed characterization of the molecular structure under different conditions. Using 1D and 2D 1H NMR studies we are establishing that MKs have different conformations depending on the specific environmental conditions. Similarly, we show using 1H-1H 2D NOESY NMR studies that the association of MK with the surfactant- water interface of reverse micelles, which is a model membrane system, modify the conformation of the menaquinone derivative. Finally, the redox potentials of MK-2 was measured in the three different solvents (DMSO, CH3CN and pyridine). We hypothesize that the redox potential is correlated to the conformational of the MK. We observed that the redox potentials varied with solvent. The observed folded structures of MK derivatives stand in contrast to the linear conformation shown in life science text books
siRNA nanoparticle functionalization of nanostructured scaffolds enables controlled multilineage differentiation of stem cells
No full textThe creation of complex tissues and organs is the ultimate goal in tissue engineering. Engineered morphogenesis necessitates spatially controlled development of multiple cell types within a scaffold implant. We present a novel method to achieve this by adhering nanoparticles containing different small-interfering RNAs (siRNAs) into nanostructured scaffolds. This allows spatial retention of the RNAs within nanopores until their cellular delivery. The released siRNAs were capable of gene silencing BCL2L2 and TRIB2, in mesenchymal stem cells (MSCs), enhancing osteogenic and adipogenic differentiation, respectively. This approach for enhancing a single type of differentiation is immediately applicable to all areas of tissue engineering. Different nanoparticles localized to spatially distinct locations within a single implant allowed two different tissue types to develop in controllable areas of an implant. As a consequence of this, we predict that complex tissues and organs can be engineered by the in situ development of multiple cell types guided by spatially restricted nanoparticles
Mitigating the autogenous shrinkage of alkali-activated slag by metakaolin
No full textThis study investigates the effectiveness of metakaolin (MK)in mitigating the autogenous shrinkage of alkali-activated slag (AAS). It is found that the autogenous shrinkage of AAS paste can be reduced by 40% and 50% when replacing 10% and 20% slag with MK, respectively. By providing additional Si and Al, and decreasing the pH of the pore solution, the incorporation of MK retards the formation of aluminium-modified calcium silicate hydrate (CASH)gels, the main reaction products in the studied pastes. The chemical shrinkage and pore refinement are consequently mitigated, resulting in a substantial reduction in the pore pressure. Meanwhile, the elastic modulus of AAS paste is only slightly influenced after MK addition. As a result, the autogenous shrinkage of AAS is significantly mitigated by incorporating MK. In addition, the introduction of MK would extend the setting time, slightly decrease the compressive strength, but greatly increase the flexural strength of AAS.Accepted Author ManuscriptMaterials and Environmen
Dialogue with the text (Mk 3:20f, 31-35) : interactional Bible interpretation
No full textCITATION: Dormeyer, D. 1990. Dialogue with the text (Mk 3:20f, 31-35) : interactional Bible interpretation. Scriptura, 33:55-64, doi:10.7833/33-0-1882.The original publication is available at http://scriptura.journals.ac.zaThe article explains some basic concepts and procedures of ‘interactional Bible interpretation’, a novel approach developed by the author. The method is illustrated by applying it to the narrative of Mk 3:20f and 31-35, in which the concept of Jesus’ family is developed as a new metaphor. What is presented here is based on a series of guest lectures by the author at the University of Stellenbosch in 1988.https://scriptura.journals.ac.za/pub/article/view/1882Publisher's versio
A BJT-Based Temperature-to-Digital Converter with ±60 mK (3 σ) Inaccuracy From-55 °c to +125 °c in 0.16-μm CMOS
No full textThis paper presents a precision CMOS temperature-to-digital converter (TDC), which senses the temperature-dependent base-emitter voltage of substrate PNPs. Measurements on 20 samples from one batch show that it achieves an inaccuracy of ±60 mK (3σ) from-55 °C to +125 °C, after a single room-temperature trim. This state-of-the-art result is mainly due to the extensive use of dynamic error cancellation techniques to generate the PNP's collector currents, thus minimizing the spread in their base-emitter voltages, together with a digital PTAT trim to correct for the spread in the PNP's saturation currents. The effect of process variation on the TDC's inaccuracy was investigated by measuring 80 samples from three different batches. Using the same calibration parameters, they exhibit a maximum untrimmed inaccuracy of ±2 °C (3σ) from-55 °C to +125 °C. This drops to ±100 mK (3σ) after a single point trim. The proposed TDC thus reduces calibration costs by obviating the need for batch-specific calibration parameters, which would otherwise require the multipoint calibration of several samples. The effect of the PNP's current gain β was also investigated with the help of a novel β-detection circuit. Implemented in 0.16-μm CMOS, the TDC occupies 0.16 mm2 and draws 4.6 μA from 1.5 to 2 V supply voltages. It achieves a resolution Figure of Merit of 7.8 pJ°C2, and a state-of-the-art supply sensitivity of 0.01 °C/V.Accepted Author ManuscriptElectronic InstrumentationMicroelectronic
- …
