No description available.

The reproductive biology of a pride of lions (Panthera leo) was studied on the 8500 ha Karongwe Game Reserve from 1999 to 2005. Over this period, the pride consisted of between four and 11 lions with a paired coalition of adult males during the first three years and a single adult male for the next three years.We recorded shorter than normal interbirth intervals, high birth rates of 1.3 cubs/lioness/year, very high cub survival rates, and subadults leaving the pride at young ages. This translated into substantially faster growth rates than are typical in large lion populations in ecologically similar circumstances such as Kruger National Park, but are similar to those of lions in Serengeti National Park. These demographic characteristics were probably induced initially by a lack of intense intraspecific competition and high prey availability, but population stability was maintained through the removal of young subadults by management. Interestingly, variability in conception rates between lionesses resulted in lower growth rates than have been found in other similar reintroduced lion populations. These demographic traits characterize many of the small reintroduced lion populations, and call for appropriate management to avoid the consequences of high predator densities.

Battery-powered portable embedded systems have been widely used in many applications. These embedded systems have to concurrently perform a multitude of complex tasks under stringent time constraints. As these systems become more complex and incorporate more functionality, they became more power-hungry. Thus, reducing power consumption and extending battery lifespan while guaranteeing the timing constraints has became a critical aspect in designing such systems. This gives rise to three aspects of research: (i) Guaranteeing the execution of the hard real-time tasks by their deadlines, (ii) Determining the minimum voltage under which each task can be executed, and (iii) Techniques to take advantage of run-time variations in the execution times of tasks. In this research, we present techniques that address the above aspects in single and multi processor embedded systems. We study the performance of the proposed techniques on various benchmarks in terms of energy savings.

Proper speaking rate is a key attribute of effective communication. Emerging persuasive technologies use computers as a tool to induce human behavioural and attitude changes. This thesis established a computational framework which can persuade people to slow down their speech and communicate more effectively. We defined a conceptual model and implemented a computer software system, both serving as the cornerstones of our persuasion framework. The computer system is designed to persuade people to be aware of their speaking rate and to slow down their speech. The combination of computer technology and persuasive technologies and theories are embedded in the system. In order to conduct effective persuasion, a number of computer-based survey questions were asked and a short tailored letter was generated for each participant. A virtual coach system monitored and reminded the participant to slow down. A few adaptive cues were used to enhance the effects of the persuasion. We evaluated the feasibility and effectiveness of the overall system. At the same time, we evaluated the feasibility of individual elements. A total of 22 participants was selected to make up the sample. The experiments were conducted under controlled conditions. The results indicated that our system is effective in persuading people to speak more slowly. The feedback from users indicated that our system raised their awareness about speaking rate.

Submerged sediment-laden ice blocks that form on the intertidal mud flats of the Minas Basin pose a potential threat to tidal turbines planned for deployment in the Minas Passage. Laboratory prepared ice blocks of varying sediment content, salinity, and length scale were melted in seawater of different temperatures. The effect of sediment inclusions on melt rate is related to changes in heat supply and the heat required to melt a unit mass of ice, where the former is affected by the strength of the convective current and the latter by the ice block properties. A melt rate model for submerged sediment-laden ice is developed, with free convection the dominant deterioration mechanism. The model provides probable upper limits to the lifetimes of submerged ice blocks in the field, and has been used to predict lifetimes of large submerged ice blocks using temperatures representative of seawater in the Minas Basin.

With the focus of the automotive industry on decreasing vehicle weight and improving fuel efficiency, aluminum is being used for structural components in automobiles. Given the high strain rates associated with vehicle impact, it is necessary to understand the rate sensitivity of any potential alloy (eg. AA5754) in order to accurately predict deformation behaviour. Furthermore, the magnitude and strain path associated with the residual strains remaining after forming of the component also play a major role in how the material will behave. It has been found that AA5754 sheet exhibits negative rate sensitivity up to a strain rate of 0.1/s, and positive strain rate sensitivity at strain rates between 0.1/s and 1500/s. Increasing the strain rate also has the effect of increasing the yield stress as well as the ductility. When a strain path change is involved between the prestrain stage and subsequent uniaxial loading, it has the effect of reducing the rate sensitivity of the material as well as reducing the overall flow stress. A rate-sensitive adaptation of the Voce material model was successfully implemented in LS-DYNA and used to predict the response of AA5754 sheet in bending for applied strain rates of 0.001/s and 0.1/s. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2008-09-23 20:11:30.829

Failure of metals under impact loading is known to occur through the formation of adiabatic shear bands (ASBs). ASBs appear in materials as evidence of damage, and are known to be sites for material failure. General purpose plasticity models fail to predict the phenomenon of ASB formation. The present research validates and extends a model developed at the University of Manitoba by Feng and Bassim to predict damage due to ASBs. Parameters for the Feng and Bassim model are determined experimentally using a direct impact pressure bar to impact specimens at temperatures of 20-500oC and strain rates of 500-3000/s. A direct impact experiment is simulated in ANSYS using the model and fitted parameters. The results of the simulation show localized temperature rise and predict failure at the same locations as those observed experimentally. Nominal strain to failure is approximately 40-50% for a specimen impacted at 38 kg-m/s.

Volumetric modulated arc therapy (VMAT) is an efficient and conformal radiation therapy technique. It accomplishes this by dynamically varying multi-leaf collimator (MLC) positions, dose rates and gantry velocity. This work investigated the effect of varying the maximum MLC speed and maximum dose rate on the quality, efficiency and accuracy of treatment plans. The Pinnacle3 SmartArc treatment planning software was used to generate plans on prostate and head and neck (H&N) sites. A range of maximum MLC leaf speeds (0.55 cm/s to 2.20 cm/s) and maximum dose rates (200 MU/min to 600 MU/min) restrictions were applied to each plan to investigate their effect on the treatment quality, efficiency and accuracy. Each plan had their monitor units (MU) per fraction, delivery time, mean dose rate and leaf speed analysed. The dose volume histogram (DVH) data was used in the assessment of the conformity, homogeneity and plan quality. The treatments were delivered on Varian iX accelerator equipped with 120-leaf millennium MLC. Quality assurance measurements were performed using the ArcCHECK™ 3D diode array and results were assessed based on gamma analysis of dose fluence maps, beam delivery statistics and Dynalog data. The number of VMAT fields was found to be a key factor in how significant the maximum MLC leaf speed affected the plan parameters investigated. Single arc treatments were shown to have lower MU, dose rate and plan quality, while also exhibiting a slight increase in estimated delivery time. For dual arc treatments, MU, delivery time, dose rate and plan quality were largely independent of the maximum MLC speed allowed. The QA showed that higher MLC leaf speeds were prone to an increase in the discrepancy between planned and delivered control point (CP) fluence and higher MLC positioning errors. None of these were at a clinically significant level, and the overall fluence distribution and point dose comparisons were independent of maximum MLC leaf speed. The only clinically significant effect that modulation of the maximum dose rate had was on the delivery time. Lower maximum dose rates resulted in longer treatment delivery, which is an important consideration in minimising the intra-fractional motion during treatment. The results of the MLC leaf speed evaluation showed that the lower the maximum leaf speed the more accurate the delivered treatment, -however the quality of the plan is reduced. This indicates that there could be an optimum maximum MLC leaf speed which produces high quality plans that can be accurately delivered. Based on this work a maximum MLC leaf speed of 1.38 cm/s was shown to have no reduction in plan quality however it showed improvement in delivery accuracy. There was no justification found for reducing the maximum dose rate below the recommended 600 MU/min.

No description available.

As multiple trauma is ubiquitous, affects predominantly young people and is attended by a high mortality, it seemed a fruitful area for study in an effort to reduce morbidity and mortality. One of the main problems in trauma research has been accurate description of the severity of injury and associating severity with subsequent outcome. While a number of scoring systems have been proposed the Injury Severity Score has been the most widely adopted and validated. The Injury Severity score was adopted with a number of other systems of scoring infection and other complications in a retrospective study of multiple trauma patients admitted to an Intensive Therapy Unit. This study revealed an unexpected increased in mortality in the latter two years of the study period which was not associated with an increase in injury severity as assessed by the ISS nor by any other change in patient characteristics which might explain this finding. Eventually it was noted that the introduction of a hypnotic drug etomidate for use in sedation of ventilated patients seemed to be associated with the increased mortality. Clinical evidence suggested that etomidate might inhibit adrenocortical function and an experimental study indeed confirmed that etomidate had a direct effect on adrenal steroidogenesis such that cortisol and aldosterone production were completely suppressed. Following analysis of the retrospective clinical study etomidate was withdrawn from use in our unit. Analysis of mortality rates both for trauma patients and the general patient population indicated a reversion to the rate which pertained prior to introduction of etomidate. The results of retrospective and prospective clinical studies strongly implied that the administration of etomidate was associated with an increased mortality among trauma patients. The experimental study based on clinical observations clearly demonstrated that etomidate infusion was a potent inhibitor of adrenal steroidogenesis. It seems highly likely that the detrimental effect of etomidate was mediated by its direct inhibitory effect on the production of cortisol and aldosterone by the adrenal gland. Subsequent clinical and experimental studies from other authors tend to confirm these findings.