This thesis comprises a series of independent investigations examining rugby injuries occurring to players from under 14 to senior provincial level in the Cape Province (now the Western Cape). The first two studies report data aimed at gaining a more detailed understanding of rugby injuries in specific populations or under specific conditions, whilst the remainder of the thesis reports injury data from both a retrospective and a prospective epidemiological survey involving the same 3990 boys from 25 high schools. Following publication of data showing a progressive rise in the number of spinal cord injuries in the Western Cape, coupled with a sustained media attack on the attitudes of the (then) South African Rugby Board, certain experimental law changes were introduced to South African schoolboy rugby in 1990 and 1991. The purpose of the law changes was either to make the game safer or to make it more open and flowing, or both. Accordingly, the studies described in chapters 4 -8 set out to analyse the effects of these law changes on the incidence and nature of rugby injuries. This was accomplished by comparing data with a similar study conducted in 1983 and 1984 in the same 25 schools (Roux, 1992). The study reported in chapter 2 determined whether the use of neoprene (thermal) pants might reduce the risk of hamstring injury amongst 60 senior club rugby players, all of whom had previously sustained a hamstring muscle tear. The rationale was that the few seasons prior to this 1992 study had been characterised by an increasing use by rugby players of thermal or neoprene pants; a practice which seemed to have evolved spontaneously and without any scientific assessment of its value. We concluded that the wearing of thermal pants can reduce the risk of hamstring injury during rugby. However, other risk factors for injury are probably more important. These include levels of preseason physical fitness, correct warm up and stretching procedures before activity and adequate rehabilitation before returning to activity following injury. The objective of the study reported in chapter 3 was to determine the influence of preseason strength and endurance training on risk of injury in rugby players from two South African provincial teams during the 1992 rugby season. Players from one province followed a supervised scientifically-designed physical training programme, while those from the other did not follow a structured programme. The findings of the study, the first study to prove the relationship between pre-season preparation and early season injury, showed that inadequate pre-season endurance training is a major contributor to the high injury rate at the beginning of the season amongst provincial rugby players. Further, strength and endurance training are interrelated as risk factors. Thus, compared to players with adequate strength and endurance training, those with adequate strength training and insufficient endurance training are at greatest risk of injury, followed by players with insufficient strength and endurance training. It was also shown that contact practices 2 days after inter-provincial match contributed more to an increased number of injuries than to success; that "niggling" injuries may develop into more serious injury if players attempt to "play through" them; and that the lack of structured treatment and rehabilitation of an injury places players at risk of being re-injured.

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This dissertation explores various topics within the theme of nanostructured polymer electrolyte membranes having controlled morphology, and their resulting properties. Chapter 1 gives an introduction to the field of Polymer electrolyte membranes (PEM) in its current state, and an overview of the work done. In chapter 2, relatively inexpensive block copolymer ionomers of fluorinated poly(Isoprene)-block-sulfonated poly(Styrene) (FISS) with various sulfonation levels, in both the acid form and the cesium neutralized form, have been cast into membranes of desired random phase separated morphology. The morphology of these membranes were characterized by TEM and USAXS, as well as water uptake, proton conductivity and methanol permeability from 20 to 60°C. The transport properties increased with increasing sulfonation and temperature for all samples. The acid form samples absorbed more water than the cesium samples with a maximum swelling recorded at 60°C for the acid sample with 50mol% sulfonation. Methanol permeability for the latter sample was more than an order of magnitude less than Nafion 112 but so was the proton conductivity at 20°C within the plane of the membrane. Across the plane of the membrane this sample had half the conductivity of Nafion 112 at 60°C. In chapter 3, neutron and x-ray scattering techniques have been used to study the structural evolution of FISS materials as they have evolved from the dry state to the water soluble state. A dilation of the nanometer-scale hydrophilic domains have been observed as hydration has been increased, with higher swelling for the higher sulfonated sample or upon hydrating at higher temperatures. Furthermore a decrease in the order in these phase separated structures is reduced upon swelling. The glass transition temperature of the fluorinated blocks decreased upon hydration, and at the highest hydration levels loosely bound water was evident. Thermal and dynamic mechanical characterization of these materials have shown that there is a high degree of softening beyond the 45°C glass transition temperature. Finally highly sulfonated samples have shown the formation of spherical micelles, even at concentrations as low as 0.05 mg/ml. The sizes of these micelles range from 13–13.5 nm, with the higher concentration solutions having smaller radius of gyration, possibly due to crowding effects. In chapter 4, Ionomers from the cesium salt (20 mol%) of fluorinated Poly(Isoprene)-block-sulfonated Poly(Styrene) have been spun cast into membranes and annealed under an electric field of ∼40 V/um at 130°C for 24 hours. This resulted in the transformation of the morphology from a random phase separated state to one preferentially oriented in the direction of the electric field but with smaller domain sizes. The effect of this change in morphology was a 2.5 times increase in the ionic conductivity, as measured by electrochemical impedance spectroscopy, at all humidity conditions measured. This can be attributed to the increased connectivity of the ionic domains. In chapter 5, The applicability of electrospun nanostructure with high surface to volume ratios for PEM application is presented. To this end, sulfonated poly(ether ether ketone) has been electrospun and electrosprayed by varying concentration in DMF, yielding isotropic fibrous mats and beads. The glass transition temperatures of these materials have been shown to be higher those of the unsulfonated precursors and they increase with increasing sulfonation, due to hydrogen bonding induced rigidity. The presence of sulfonic acid groups on the surface has been confirmed by means of x-ray photoelectron spectroscopy, with sulfur representing 3% of the surface elemental composition. These acid groups on the surface of internal fibers, help to form a 3 dimensional network of conducting channels in the voids of the fibrous mats upon hydration. This in turn has led to an improvement of conductivity from 0.033 S/cm for void-less solution cast membranes to 0.040 S/cm for the electrospun fibrous mats.

With an overwhelming volume of news reports currently available, there is an increasing need for automatic techniques to analyze and present news to a general reader in a meaningful and efficient manner. Previous research has focused primarily on organizing news stories into a list of clusters by the main topics that they discuss. We believe that viewing a news topic as a simple collection of stories is restrictive and inefficient for a user hoping to understand the information quickly. As a proposed solution to the automatic news organization problem, we introduce incident threading in this thesis. All text that describes the occurrence of a real-world happening is merged into a news incident, and incidents are organized in a network with dependencies of predefined types. In order to simplify the implementation, we start with the common assumption that a news story is coherent in content. In the story threading system, a cluster of news documents discussing the same topic are further grouped into smaller sets, where each represents a separate news event. Binary links are established to reflect the contextual information among those events. Experiments in story threading show promising results. We next describe an enhanced version called relation-oriented story threading that extends the range of the prior work by assigning type labels to the links and describing the relation within each story pair as a competitive process among multiple options. The quality of links is greatly improved with a global optimization process. Our final approach, passage threading, removes the story-coherence assumption by conducting passage-level processing of news. First we develop a new testbed for this research and extend the evaluation methods to address new issues. Next, a calibration study demonstrates that an incident network helps reading comprehension with an accuracy of 25-30% in a matrix comparison evaluation. Then a new three-stage algorithm is described that identifies on-subject passages, groups them into incidents, and establishes links between related incidents. Finally, significant improvement over earlier work is observed when the training phase optimizes the harmonic mean of various evaluation measures, and the performance meets the goal in the calibration study.

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As the use of concurrent and concurrent real-time software systems in safety-critical applications becomes widespread, the verification of their correctness has become an important concern. Unfortunately, analysis of these systems has been stymied by the explosive number of states they possess. The constrained expression approach, which uses an inequality-based technique to avoid the enumeration of these states, showed promise for analyzing large systems, but was incapable of verifying many important properties of interest to designers. For example, properties involving the order of the events in a concurrent system (e.g., mutual exclusion) could not be verified since the inequalities did not capture this information, nor could the technique verify liveness properties, since these require reasoning about infinite executions. I have developed extensions to this inequality-based technique that allow the verification of these more complex properties. In addition, I have completely automated an earlier extension of this technique for deriving bounds in concurrent real-time systems run on a uniprocessor and I have extended this technique to the maximally-parallel multiprocessor setting. Most importantly, I have demonstrated the feasibility of these extensions by implementing them in an automated tool and using this tool to analyze several sample systems.

This dissertation addresses the dichotomy between semantic and episodic knowledge by focusing on the evolution of scientific knowledge. Even timeless scientific knowledge about the nature of the world accrues only through discrete episodes, with each scientist building upon the work of his/her predecessors. Hence, a memory organization to model the knowledge of a scientific field should reflect not only the knowledge pertaining to the field, but also the knowledge pertaining to the evolution of the field. A computer program called RA is described: RA proposes a memory organization for scientific knowledge in terms of a representational idea called Research Schemas. Research Schemas view research papers, not as isolated pieces of text, but as related episodes that contribute to the growth of a scientific discipline. This memory organization is validated by showing that it supports a number of different capabilities: it enables RA to suggest new research directions, acquire new research schemas, retrieve papers that have similar research strategies, and generate both chronological and analogical summaries of research papers. A combination of these capabilities constitutes a framework for 'Computer-Aided Research.' The RA system also includes a learning technique to acquire new research schemas. While similarity-based techniques use multiple examples (and some form of encoded bias) and explanation-based techniques use a domain theory as the basis for generalization, there is no apparent basis for RA's generalization. An analysis of RA's learning strategy shows that the category structure of RA's world provides a basis for its generalization: RA generalizes instantiations into categories that are both associative and discriminative. Interestingly, this turns out to be precisely the property that characterizes basic-level categories that have been studied by psychologists. This dissertation explores the implication of this results to learning and knowledge representation.

The idea of a feminist science has been treated as settled knowledge. Philosophers of science have, implicitly or explicitly, defined it as a science guided by feminist values. For a long time, feminist philosophers were concerned with defending its conceptual possibility (Longino, 1987), and they largely succeeded; the value-free ideal is in retreat (Holman and Wilholt, 2022). But now that they may finally unclench from their defensive posture, what comes next for their positive program to theorize feminist science? The dissertation takes up this question and attempts to clarify and advance new research questions. I ask: what follows if we take seriously the constraints under which feminist scientists must labor? Which values in science are feminist? What does it mean for science to be ‘value-laden’? Are feminist values epistemically or normatively indispensable? If not, how do we justify the importance of doing science as a feminist?

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No description available.