MIXTURE MODELING WITH APPLICATIONS IN ALZHEIMER\u27S DISEASE

This dissertation involves an application of mixture of regression models to 114 individuals who are cognitively intact (from the Alzheimer\u27s Disease and Neuroimaging Initiative-ADNI, data). The correct number of components in the model were estimated with the Singular BIC (SBIC), marking the first time it has been applied to such a problem. The smallest true model in conjunction with the approximation of SBIC was fixed at 1. The resulting posterior probabilities from the model were used to estimate the probability of a person transitioning and risk plots were obtained that could in principle be used by clinicians to identify patients at risk. This work also proposed a model selection criterion for mixture of regression models with application to the ADNI data. Finally simulation studies were conducted to compare the performance of the novel model selection and existing criteria

Interconnectedness of technology teachers’ perceptions of the design process to learner creativity

The design process (DP) is key to technology education and is considered as synonymous with problem solving, hence it undergirds all its learning aims and objectives. The Curriculum Assessment and Policy Statement (CAPS) document envisages that the design process will promote problem solving, critical thinking and creativity in learners. However, a paucity of empirical studies within the South African context illuminates the interconnectedness of DP to problem solving, critical thinking and creativity in learners for which the CAPS policy advocates. Further, there is a need to explore the interconnectedness of teachers’ perceptions of the DP, their enactment of the DP and its impact on learner creativity. This paper reports on a study that explored that interconnectedness and addressed the following research questions: What are grade 9 technology teachers’ perceptions of the design process? How do these perceptions relate to teachers’ reported enactment of the DP and creativity in learners? The conceptual framework used to model the interconnectedness that exists between teachers’ perceptions and reported enactment of the design process is Shulman’s pedagogical content knowledge model (PCK). This interpretivist study was located in the Umlazi district of KwaZulu-Natal. A case study design was used to collect qualitative data via an open-ended questionnaire and a semi-structured interview from 30 purposively selected technology teachers. Content analysis of data was undertaken in line with the conceptual framework. Our findings reflect that teachers’ perception and reported enactment of DP and the flexibility of the learning environment have an impact on opportunities for problem solving, critical thinking and creativity in learners. Our findings raise questions about the type of professional development teachers need to enact the envisaged goals of the CAPS document in respect of the DP in technology education

Teaching the design process in the grade 9 technology class.

M. Ed. University of KwaZulu-Natal, Durban 2014.The design process undergirds technology education and therefore it is quintessential to the teaching, learning and assessment of technology education. Since the introduction of technology education into the South African curriculum, there has been a series of changes that teachers have had to contend with: C2005, RNCS and now the NCS-CAPS. In the CAPS technology policy there has been a (re)-presentation of the design process from a linear to nonlinear. This (re)presentation of the design process has led to uncertainties amongst teachers of technology in terms of how the teaching of the design process should unfold. This study therefore explores grade 9 technology teachers’ views of the design process and how these views influence their teaching of the design process. Shulman’s Pedagogical Content Knowledge (PCK) model (1986), the Argyris and Schön (1974) notion of “espoused theory” and “theory in use”, and Singh-Pillay’s (2010) notion of interface have been used to frame the research. A qualitative case study approach was used. Purposive and convenience sampling were used to obtain the respondents for this study. An open ended questionnaire, semi-structured interviews, observation of lessons and post-observation interviews were used to collect data. The study occurs in the Chatsworth West ward in Durban, KwaZulu Natal. The findings indicate that grade 9 technology teachers hold two core views of the design process, namely: design process as problem-solving and design process as a step-by-step process that provides “comfort” to learners during problem-solving. The findings indicate that teachers’ views of the design process are an amalgam of their diverse qualification in technology education, their pedagogical content knowledge, their previous teaching experience, their training and (re)training and iv existing support in the school ecosystem. Thus, it is concluded that the PCK of the technology teacher influences how they teach the design process to their learners. It is recommended that if the non-linear approach of problem-solving in the design process is to be adhered to then there is the need for the retraining and reskilling of technology teachers and that teacher education should also focus more on the development of the PCK of future teachers

Old timber plantations and secondary forests attain levels of plant diversity and structure similar to primary forests in the West African humid tropics

Considering the high rate of primary forest degradation and loss in the tropics, the ability to conserve plant diversity within alternative forest landscape components is critical to biodiversity conservation. This study compares the restoration potential of old forest plantations and secondary forests. We assessed and compared the floristics, plant species diversity, conservation value, and structure of old (42-47 years) timber plantations of Aucoumea klaineana Pierre, Cedrela odorata L., Tarrietia utilis Sprague, and Terminalia ivorensis A. Chev. and similar-aged secondary forests with nearby primary (old-growth) forests in the moist and wet forest zones of Ghana. We established a systematic sampling set-up of ninety-three 20 m x 20 m plots in total on 11 sites, with smaller nested subplots for saplings and ground vegetation. The floristic composition of the plantation and secondary forest stands were similar to that of the primary forests, with many rare and restricted-range species shared by the three forest types. Approximately 77% and 60% of primary forest plant species also occurred in plantation and secondary forests, respectively. Species diversity, measured by the Shannon-Wiener Diversity Index (H') and Simpson Index (S), for the primary forest (H'=3.07, S = 0.91) was not statistically different from the plantation (H'=2.85, S = 0.87) or secondary (H'=2.95, S = 0.88) forests. Overall, species richness was higher in the primary and secondary forests compared to the plantations. At the tree stratum (>= 10 cm DBH), the assessed diversity indices were significantly different between the primary forest and the plantations. However, such differences did not exist among the saplings (10 cm > DBH >= 2 cm) and ground vegetation (< 2cm DBH). The plantations and secondary forests were similar to the primary forests for all the structural characteristics assessed. However, basal area and bole volume were significantly higher in the plantations compared with secondary forests. Conservation value (using Genetic Heat Index as an indicator) was highest in one of the C. odorata plantations (W-CO). Our study demonstrates that plantation and secondary forests can develop into structurally complex and floristically diverse self-organized stands similar to primary forests. Passive conversion of plantations to more natural ecosystems is an effective and low-cost forest restoration strategy leading to diverse ecosystems with high conservation value.Peer reviewe

Consumer Choice Analysis of Imported and Locally Produced Chicken Products: Evidence from Ghana.

An understanding of why a person makes purchasing is very important in the marketing process of those consumers located at Kumasi metropolis. The paper investigated into consumer choice analysis of imported and locally produced chicken in Kumasi metropolis. Of which convenience sampling was used to select the sample size of three hundred and fifty (350) respondents to answer the questionnaires. The study revealed that influence of price on purchasing decision was high. Also issues of   quality had poor influence in the purchasing decision of chicken products thus accounting for the higher rate of neutrality of respondents view in that regard. In addition, the study showed that participants responded to all the elements on the influence of quality on the demand for chicken products in the Kumasi metropolis, as well as influence of quantity on the demand and purchase for chicken products. The recommendations are based on the weaknesses identified in the study:  effect of price, quality and quantity. It is believed that the recommendations such as ensuring effective competitive price for locally produced chicken by providing adequate and readily funding for farmers. Also, improving the packaging of the locally produce chicken to be at par with an international standard. These will help to improve the bottlenecks associated with the production of locally produced chicken. Key words: Consumer; Purchasing; Behaviour; Decision makin

Above-ground carbon stocks and timber value of old timber plantations, secondary and primary forests in southern Ghana

High deforestation rates, especially in the tropics, currently result in the annual emission of large amounts of carbon, contributing to global climate change. There is therefore an urgent need to take actions to mitigate climate change both by slowing down deforestation and by initiating new sinks. Tropical forest plantations are generally thought to sequester carbon rapidly during the initial years but there is limited knowledge on their long-term potential. In this study, we assessed the carbon sequestration in old (42-47 years) timber plantations of Aucoumea klaineana, Cedrela odorata, Tarrietia utilis, and Terminalia ivorensis, and secondary forests of similar ages, by comparing their basal areas and above-ground carbon stocks (AGC) to that of nearby primary forests. Additionally, we estimated and compared timber volume and stumpage value in the three forest types. Systematic random sampling of ninety-three 20 m x 20 m plots in eleven forest sites (2 secondary forests, 2 primary forests, and 7 timber plantations) was undertaken to determine the effect of forest type on AGC, basal area, timber volume, and stumpage value. After 42 years of growth, mean AGC of the timber plantations (159.7 +/- 14.3 Mg ha(-1)) was similar to that of primary forests (173.0 +/- 25.1 Mg ha(-1)) and both were significantly higher than the mean AGC of the secondary forests (103.6 +/- 12.3 Mg ha(-1)). Mean basal area and timber volume of the timber plantations and secondary forests were similar to that of the primary forests, though in each case the timber plantations had significantly higher values compared to the secondary forests. Mean timber value of the plantations ($8577 ha(-1)) was significantly higher than both secondary ($1870 ha(-1)) and primary forests ($3112 ha(-1)). Contrary to our expectations, naturally regenerated trees (woody recruits) within the timber plantations had similar AGC levels, basal area, timber volume, and value compared to the secondary forests. Long-rotation tropical forest plantations under low-intensity management could achieve higher AGC levels and thus have higher climate change mitigation potential and timber values compared to naturally regenerated secondary forests, and are able to reach values similar to primary forests. Monoculture timber plantations could facilitate the successful colonization of their understoreys by native woody recruits that contribute considerably to stand AGC and timber values. Long-rotation forest plantations in the tropics therefore have a critical role to play in forest rehabilitation and climate change mitigation while having the potential to provide modest financial returns to landowners through selective harvesting of timber and/or payments for carbon sequestration.Peer reviewe

The changing epidemiology of esophageal cancer in sub-Saharan Africa – the case of Ghana

Introduction: Esophageal cancer portends a grim prognosis. Most patients present with incurable disease. Scanty epidemiologic data on the disease has contributed to its low priority on the national. We sought to evaluate the current national trend in the presentation and outcome of esophageal cancer using our institutional experience from 1992 – 2010. Methods: This is a retrospective study based on 152 patients who were seen in our institution during the study period. The perioperative data of these patients were retrieved and the relevant details recorded. Histopathological reports were available for 75 patients managed over the period. The study setting was The National Cardiothoracic Centre, which serves as the only tertiary referral centre in the country for cardiothoracic problems. Results: There were 122 males and 30 females with a mean age of 57.8±11.7 years. The yearly trend from 1992 to 2010 showed a steady increase in the incidence of esophageal cancer. High alcohol consumption and smoking dominated the history of 82.2% of the patients. Squamous cell carcinoma accounted for 78.7% and adenocarcinoma 21.3%. Distribution of esophageal carcinoma by anatomical location was 84.9% for distal third, 11.8% for middle third and 3.3% for upper third. All patients presented with incurable disease. Conclusion: The study shows an increasing incidence of esophageal carcinoma in this country. Alcohol abuse and smoking are major risk factors; squamous cell carcinoma is the dominant histological type in this study.Pan African Medical Journal 2012; 13:

The Use of Intraosseous Needles for Injection of Contrast Media for Computed Tomographic Angiography of the Thoracic Aorta

Background The objective of this study is to evaluate the safety and quality of computed tomographic angiography of the thoracic aorta (CTA-TA) exams performed using intraosseous needle intravenous access (ION-IVA) for contrast media injection (CMI). Methods All CTA-TA exams at the study institution performed between 1/1/2013 and 8/14/2015 were reviewed retrospectively to identify those exams which had been performed using ION-IVA (ION-exams). ION-exams were then analyzed to determine aortic attenuation and contrast-to-noise ratio (CNR). Linear regression was used to determine how injection rate and other variables affected image quality for ION-exams. Patient electronic medical records were reviewed to identify any adverse events related to CTA-TA or ION-IVA. Results 17 (∼0.2%) of 7401 exams were ION-exams. ION-exam CMI rates varied between 2.5 and 4 ml/s. Mean attenuation was 312 HU (SD 88 HU) and mean CNR was 25 (SD 9.9). A strong positive linear association between attenuation and injection rate was found. No immediate or delayed complications related to the ION-exams, or intraosseous needle use in general, occurred. Conclusion For CTA-TA, ION-IVA appears to be a safe and effective route for CMI at rates up to 4 ml/s

A cross-sectional study on the co-occurrence of infectious diseases, malnutrition and cardio-metabolic risk factors

In sub-Saharan Africa, infectious diseases and malnutrition constitute the main health problems in children, while adolescents and adults are increasingly facing cardio-metabolic conditions. Among adolescents as the largest population group in this region, we investigated the co-occurrence of infectious diseases, malnutrition and cardio-metabolic risk factors (CRFs), and evaluated demographic, socio-economic and medical risk factors for these entities. In a cross-sectional study among 188 adolescents in rural Ghana, malarial infection, common infectious diseases and Body Mass Index were assessed. We measured ferritin, C-reactive protein, retinol, fasting glucose and blood pressure. Socio-demographic data were documented. We analyzed the proportions (95% confidence interval, CI) and the co-occurrence of infectious diseases (malaria, other common diseases), malnutrition (underweight, stunting, iron deficiency, vitamin A deficiency [VAD]), and CRFs (overweight, obesity, impaired fasting glucose, hypertension). In logistic regression, odds ratios (OR) and 95% CIs were calculated for the associations with socio- demographic factors. In this Ghanaian population (age range, 14.4–15.5 years; males, 50%), the proportions were for infectious diseases 45% (95% CI: 38–52%), for malnutrition 50% (43–57%) and for CRFs 16% (11–21%). Infectious diseases and malnutrition frequently co-existed (28%; 21–34%). Specifically, VAD increased the odds of non-malarial infectious diseases 3-fold (95% CI: 1.03, 10.19). Overlap of CRFs with infectious diseases (6%; 2–9%) or with malnutrition (7%; 3–11%) was also present. Male gender and low socio-economic status increased the odds of infectious diseases and malnutrition, respectively. Malarial infection, chronic malnutrition and VAD remain the predominant health problems among these Ghanaian adolescents. Investigating the relationships with evolving CRFs is warranted