Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging method that is used in the diagnosis of many common diseases. Compared to other medical imaging modalities, MRI has the ability to provide high-resolution 2D and 3D images in arbitrary orientations, without the use of potentially damaging ionizing radiation. Myocardial perfusion MRI is a promising non- invasive clinical way to detect cardiac disease. It can also provide quantitative analysis for blood flow within the heart. However, MRI requires longer scan times to acquire images at comparable resolutions to some other imaging modalities. Increasing image resolution, both spatially and temporally, is very important to myocardial perfusion MRI. The work presented in this dissertation focuses on the development of novel dynamic contrast-enhanced (DCE) MRI that is able to achieve both high spatial and temporal resolutions, as well as suitable spatial coverage of the heart. Three novel acquisition and reconstruction frame- works are proposed and analyzed in this dissertation. The first framework we propose uses a highly undersampled 3D Cartesian acquisition and total variation (TV) constrained reconstruction to accelerate the acquisition of myocardial perfu- sion images. This technique increases temporal resolution for contrast tracking without sacrificing spatial resolution. An analysis of the effect of different k-space trajectories using this technique is performed. The purpose of the second framework is to simplify cardiac perfusion studies. An ECG- gated saturation recovery sequence is regularly used for cardiac perfusion imaging. However, using an ungated acquisition has the potential benefit of reducing the acquisition time by eliminating the need for the ECG trigger signal. We present a novel non-Cartesian 2D multi-slice ungated acquisition, and demonstrate that it is a promising alternative to ECG-gated cardiac perfusion studies. An optimization analysis of our ungated acquisition is also presented. The third method in this dissertation combines the 2D ungated acquisition with multi-band excitation, which enables the excitation of multiple slices simultaneously. This method is able to reduce scan time not only through the ungated acquisition, but also from obtaining multiple slices at once. This allows us to achieve whole heart coverage without sacrificing temporal resolution. The contributions presented in this dissertation demonstrate the basic feasibility of car- diac perfusion MRI achieving whole-heart coverage in a clinical setting by overcoming the major existing limitations: speed of acquisition and spatial coverage.

This project concerns the computational solution of inverse problems formulated as partial differential equation (PDE)-constrained optimization problems with interior data. The areas addressed are twofold. First, we present a novel software architecture designed to solve inverse problems constrained by an elliptic system of PDEs. These generally require the solution of forward and adjoint problems, evaluation of the objective function, and computation of its gradient, all of which are approximated numerically using finite elements. The creation of specialized "layered"' elements to perform these tasks leads to a modular software structure that improves code maintainability and promotes functional interoperability between different software components. Second, we address issues related to forward model definition in the presence of boundary condition (BC) uncertainty. We propose two variational formulations to accommodate that uncertainty: (a) a Bayesian formulation that assumes Gaussian measurement noise and a minimum strain energy prior, and (b) a Lagrangian formulation that is completely free of displacement and traction BCs. This work is motivated by applications in the field of biomechanical imaging, where the mechanical properties within soft tissues are inferred from observations of tissue motion. In this context, the constraint PDE is well accepted, but considerable uncertainty exists in the BCs. The approaches developed here are demonstrated on a variety of applications, including simulated and experimental data. We present modulus reconstructions of individual cells, tissue-mimicking phantoms, and breast tumors.

This thesis deals with issues of secure authentication and key management in the Internet of Things. It describes basic protocols used in IoT, cryptographic primitives, communication technologies in IoT and end elements. It also includes a measuring the performance of cryptographic primitives on Raspberry Pi and selecting the appropriate LPWAN simulation technology. The conclusion of the work is devoted to the simulation of a LoRaWAN network

The purpose of this study was to investigate parents' perceptions of the food consumption practices and nutrition-related needs in a resource-constrained community, in terms of daily eating patterns, current knowledge and attitudes with regards to food choice, food production and food preparation, as well as community-based nutrition-related needs and information to be included in an intervention aimed at community-wide health and well-being. The study forms part of a broader research project, which aims to facilitate health and well-being in resource-constrained communities, in support of reaching identified Millennium Development Goals (MDGs) and Sustainable Developmental Goals (SDGs). Interpretivism was utilised as meta-theoretical lens and a qualitative research approach was followed. I selected Bronfenbrenner's Ecosystems Theory as guiding framework for the current study. A Participatory Reflection and Action (PRA) research design was utilised to generate data with 22 purposefully selected parents from three primary schools in the Bronkhorstspruit area. Data were generated and documented through PRA-based workshops, observation, visual techniques, field notes and a reflective journal. Following inductive thematic analysis, five themes and related sub-themes emerged. The first theme relates to the daily eating patterns of the community, reflecting food consumed during breakfast, lunch and dinner. Secondly, healthy eating practices were identified as a theme, indicating that community members had a clear understanding of what healthy eating practices entails, available resources to inform healthy eating practices and current informational needs in terms of healthy eating practices. The third theme highlights food preparation practices, where women take responsibility for food preparation by means of a variety of methods. The fourth theme emphasises food purchasing practices, where community members buy from larger chain-stores, local shops and informal traders. Finally, the fifth theme indicates food production practices, where community members prefer to grow their own vegetables. Based on the findings it can be concluded that this community's food consumption patterns are primarily affected by factors in the macrosystem, namely poverty and unemployment. At the macro-level, access to healthy food, cost of healthy food and the influence of the media are aspects influencing the perceptions and decisions of community members such as parents. Changed food consumption practices and nutrition-related needs within the community may, in turn, effect change in the macrosystem by informing related future interventions. / Dissertation (MEd)--University of Pretoria, 2016. / Educational Psychology / MEd / Unrestricted

This study forms part of a broader research project that involves the investigation of the effect of a health promotion intervention (Win-LIFE) on a resource-constrained community's practices, needs and expectations related to food choice, preparation and production. As part of the Win-LIFE intervention, the South African Life Skills school curriculum was enriched, and the current study followed its implementation and focused on the experiences of 31 Grade 5 learners in a school in the Bronkhorstspruit area. For the purpose of this study I followed a qualitative methodological approach, relied on interpretivism as meta-theory and implemented a case study research design, applying Participatory Reflection and Action (PRA) principles. Data were generated by means of PRA-based activities, supported by observations, and documented through field notes, audio-visual techniques and a reflective journal. Thematic inductive analysis was completed following data generation. Four themes with related sub-themes emerged. The first theme relates to the positive experience of experiential learning. The second theme concerns the role of a supportive facilitator. The third theme entails the positive outcomes of the learning process. The last theme relates to the challenges experienced by the learners. The findings of this study indicate a positive general experience of the enriched Life Skills curriculum by the Grade 5 learners, which led to benefits both proximally and distally in the various spheres in which the learners functioned. Learners demonstrated the ability to acquire knowledge and skills in a way they enjoyed, transferred these to their families, and their motivation to learn increased. / Dissertation (MEd)--University of Pretoria, 2016. / Educational Psychology / MEd / Unrestricted

Girl youth, especially those residing in resource-constrained communities such as Diepsloot, constitute a vulnerable population group because of the daily risks they face (Watts & Zimmerman, 2002). Researchers report that chronic exposure to risks can have a negative impact on girl youth’s ability to cope and adjust (Hawke, 2000). However, interventions focused on addressing risk draw on western paradigms of resilience, not accounting for cultural aspects of resilience. Therefore, understanding how girls in Diepsloot conceptualise risk and resilience is an important step in fostering resilience among girl youth. In the present study, I draw on an ecologically-oriented systemic approach to explore how girl youth from Diepsloot make meaning of risk and resilience during an equine assisted intervention called the Growing Great Girls program. Equine assisted interventions, in particular equine assisted interventions that follow an Equine Assisted Growth and Learning Association model approach, has been found beneficial in promoting resilience among youth (Boyce, 2016). In the present study, equine assisted interventions played an important role in the process of gaining an understanding of risk and resilience from the perspectives of girl youth from Diepsloot. Using a qualitative exploratory case study design, I collected data from eight girl youth from Dieplsoot who attended the Growing Great Girls program over a period of eight weeks. From open-ended focus group interviews, photovoice, journal entries and observations as data sources, I used inductive thematic analysis to interrogate how girl youth make meaning of the risks they face to discover the source and nature of their resilience. Three themes emerged as the research results and included theme 1- individual psychosocial characteristics and family climate, theme 2- community related social issues and theme 3- broader societal issues. The findings of the present study contribute towards a broader understanding of risk and resilience that is ecologically relevant to the lives of girl youth from the Diepsloot community. / Dissertation (MEd)--University of Pretoria, 2017. / Educational Psychology / MEd / Unrestricted

The purpose of this study was to explore and describe the experiences of Grade 5 learners after being taught Natural Sciences by means of an enriched curriculum in the Win-LIFE (Wellness in Lifestyle, Intake, Fitness and Environment intervention) project. My focus thus fell on learners’ voices and perceptions, and more specifically with regard to the knowledge and skills that they gained in the Natural Sciences subject, as a result of a health-promotion intervention. For this purpose, I relied on Bronfenbrenner’s Bio-Ecological model (2005) as theoretical framework, and explored the learners’ experiences in a specific sub-system, being the Natural Sciences classroom and curriculum. I furthermore aimed to gain insight into how this can potentially be applied to other systems such as their home environments and personal lives. I used the interpretivist paradigm as meta-theory and followed a qualitative approach. I selected a case study design, applying Participatory Reflection and Action (PRA) principles, thereby aligning my study’s design to the broader research project for data generation and documentation I relied on multiple data generation sources, such as PRA-based workshops/discussions, observation, field notes, visual data documentation techniques and reflective journals to generate and document data. Following inductive thematic analysis three main themes and related subthemes emerged. Firstly, the experiential learning approach that was followed when implementing the intervention had positive outcomes in terms of learners’ attitudes toward learning, their commitment and self-confidence to make contributions in class, and their experiences of the learning process. Secondly, learners gained the necessary knowledge and skills of the Grade 5 Natural Sciences curriculum, and valued the practical experiences they acquired. In addition to their newly gained knowledge and skills being retained after a year, they finally also transferred the content to their parents, caregivers and family members, and reportedly applied what they had learned at home in their personal lives. Based on the findings of the study I can conclude that the learners experienced the enriched Natural Sciences curriculum in a positive manner and that their experiences resulted in positive outcomes and benefits for themselves and also those in their immediate environment. / Dissertation (MEd)--University of Pretoria, 2017. / Educational Psychology / MEd / Unrestricted

Full implementation of special schools converted into special school resource centres in South Africa need to be finalised by 2021, as specified in the Education White Paper 6. The purpose of special school resource centres is firstly to provide necessary resources for the education and training of learners experiencing serious barriers to learning, and secondly to provide, together with the district-based support teams, guidance and support to full-service schools and main stream schools. Despite these expectations and goals, many special schools are not fully strengthened and functional yet. Role-players involved at special school resource centres often feel unequipped to successfully manage their centres in the absence of human resources, knowledge and infrastructure. Against this background, the purpose of this study was to gain an in-depth understanding on how the asset-based approach could be utilised in supporting (or not) the more efficient functioning of a rural resource-constrained special school resource centre in the North West province, South Africa. The asset-based approach and bio-ecological model was used as conceptual framework for the study. Qualitative research was elected as methodological paradigm and an instrumental case study as research design. Interpretivism was selected as meta-theory. One rural resource-constrained special school resource centre was selected through convenience sampling, and eight participants were purposefully selected. Data was collected with individual semi-structured interviews, a focus group discussion, and observation; and documented in audio recorded verbatim transcripts, photographs, field notes and a research journal. Following thematic data analysis, three main themes emerged: identified assets and resources at the resource-constrained special school resource centre (natural assets and resources, human resources, physical resources, and resources for gardening); challenges at the resource-constrained special school resource centre (limited physical space, challenges related to the use of technology, additional responsibilities and related time constraints, and participants? location in relation to the special school resource centre); ways in which mobilised assets and resources supported the functioning of the resource-constrained special school resource centre (financial support for the special school resource centre, supporting the National School Nutrition Programme, strengthening partnerships that could support the functioning of the special school resource centre, skills development as outcome of the two asset-based projects, and intra and interpersonal qualities as a result of implementing the asset-based approach). It was therefore found that the implementation of the asset-based approach is one way to support the functioning of a resource-constrained special school resource centre. / Dissertation (MEd)--University of Pretoria, 2017. / Educational Psychology / MEd / Unrestricted

Non-facial and non-verbal methods of affective expression are essential for naturalistic social interaction in robots that are designed to be functional and lack expressive faces (appearance-constrained)such as those used in search and rescue, law enforcement, and military applications. This research identifies five main methods of non-facial and non-verbal affective expression (body movement, posture, orientation, color, and sound). From the psychology, computer science, and robotics literature a set of prescriptive recommendations was distilled for the appropriate non-facial and non-verbal affective expression methods for each of three proximity zones of interest(intimate: contact - 0.46 m, personal: 0.46 - 1.22 m, and social: 1.22 - 3.66 m). These recommendations serve as design guidelines for adding retroactively affective expression through software with minimal or no physical modifications to a robot or designing a new robot. This benefits both the human-robot interaction (HRI) and robotics communities. A large-scale, complex human-robot study was conducted to verify these design guidelines using 128 participants, and four methods of evaluation (self-assessments, psychophysiological measures, behavioral observations, and structured interviews) for convergent validity. The study was conducted in a high-fidelity, confined-space simulated disaster site with all robot interactions performed in the dark. This research investigated whether the use of non-facial and non-verbal affective expression provided a mechanism for naturalistic social interaction between a functional, appearance-constrained robot and the human with which it interacted. As part of this research study, the valence and arousal dimensions of the Self-Assessment Manikin (SAM) were validated for use as an assessment tool for future HRI human-robot studies. Also presented is a set of practical recommendations for designing, planning, and executing a successful, large-scale complex human-robot study using appropriate sample sizes and multiple methods of evaluation for validity and reliability in HRI studies. As evidenced by the results, humans were calmer with robots that exhibited non-facial and non-verbal affective expressions for social human-robot interactions in urban search and rescue applications. The results also indicated that humans calibrated their responses to robots based on their first robot encounter.

We consider constrained variants of graph homomorphisms such as embeddings, monomorphisms, full homomorphisms, surjective homomorpshims, and locally constrained homomorphisms. We also introduce a new variation on this theme which derives from relations between graphs and is related to multihomomorphisms. This gives a generalization of surjective homomorphisms and naturally leads to notions of R-retractions, R-cores, and R-cocores of graphs. Both \\mbox{R-cores} and R-cocores of graphs are unique up to isomorphism and can be computed in polynomial time. The theory of the graph homomorphism order is well developed, and from it we consider analogous notions defined for orders induced by constrained homomorphisms. We identify corresponding cores, prove or disprove universality, characterize gaps and dualities. We give a new and significantly easier proof of the universality of the homomorphism order by showing that even the class of oriented cycles is universal. We provide a systematic approach to simplify the proofs of several earlier results in this area. We explore in greater detail locally injective homomorphisms on connected graphs, characterize gaps and show universality. We also prove that for every $d\\geq 3$ the homomorphism order on the class of line graphs of graphs with maximum degree $d$ is universal.