Synthesis and investigation of the chemosensing properties of novel fluorescent triazolyl coumarin-based polymers
- Authors: Ngororabanga, Jean Marie Vianney
- Date: 2017
- Subjects: Fluorescent polymers Chemical detectors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20110 , vital:29120
- Description: Environmental pollution by ionic species has become one of the greatest challenges to the sustainable development of communities. Increasing amounts of these ionic species in the environment is associated with several detrimental effects to human health and ecological systems. Proper detection and monitoring of these ionic species is essential. Considering the diversity of the ions and the fact that the available sensors are limited, it is clear that there is need for a rapid and low-cost method for recognition and monitoring of these ions. Fluorescence based methods are ranked among the most powerful transduction systems to signal chemical recognition events. Fluorescent polymers containing triazolyl coumarin units in the polymer backbone or as pendant groups were therefore designed and investigated as potential sensors for these ions. Three methods were used to incorporate triazolyl coumarin units into the polymers. The first method involved polymerization of the vinyl monomer containing the triazolyl coumarin unit. The second method involved AA-BB step-grow click polymerization of diazide and dialkyne-functionalized monomers. The third method involved post-polymerization functionalization of an azide-functionalized polymer with an alkyne functionalized coumarin derivative. In each method, formation of the triazole ring was achieved using a Cu(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) reaction. The photophysical properties of the polymers and their starting monomers were investigated and compared. Polymers with triazolyl coumarin units in the backbone or as pendant groups were found to have higher absorption and emission intensities than their corresponding monomers while polymers resulting from functionalization of azide-functionalized polymer were found to exhibit improved photophysical properties compared to the starting azide-functionalized polymer. The chemosensing potential of the polymers was investigated through absorption and emission. The polymers were found to be selective towards different metal ions (Fe3+, Hg2+ and Al3+) and anions (-OH and F-). The mechanisms of interaction between the polymers and ions were investigated by comparing the absorption and emission spectra of the polymers to those of their monomers in the presence of an ion of interest. In some cases the mechanism of interaction was supported by 1H NMR and FT-IR.
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- Date Issued: 2017
Multiple representations and cognitive load: words, arrows, and colours when solving algebraic problems
- Authors: Brey, Amina
- Date: 2013
- Subjects: Algebraic logic , Mathematical analysis , Mathematics -- Study and teaching
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9580 , http://hdl.handle.net/10948/d1020392
- Description: This study investigates the possible effects that access to selected multiple representations (words, arrows and colours) have in terms of cognitive load and learner achievement when presented with algebraic problems at grade nine level. The presentation of multiple representations (the intervention) was intended to decrease extraneous cognitive load, manage the intrinsic cognitive load (algebraic problems) and optimise germane cognition (schema acquisition and automation). An explanatory sequential mixed-method design was employed with six hundred and seventy three learners in four secondary schools. Quantitative data were generated via pre-, intervention and post-tests/questionnaires, while qualitative data were obtained from open-ended questions in the pre-, intervention, and post-tests/questionnaires, eight learner focus group interviews (n = 32), and four semi-structured, open-ended teacher interviews. Statistically and practically significant improvement in mean test scores from the pre- to intervention test scores in all schools was noted. No statistically and practically significant improvement was noted in further post-tests except for post-test 2 which employed more challenging problems (statistically significant decrease with a small practical effect). Learners expressed their preference for arrows, followed by colours and then words as effective representations. Teacher generated qualitative data suggests that they realise the importance of using multiple representations as an instructional strategy and implicitly understand the notion of cognitive load. The findings, when considered in the light of literature on cognitive load, suggest that a reduction in extraneous cognitive load by using a more effective instructional design (multiple representations) frees working memory capacity which can then be devoted to the intrinsic cognitive load (algebraic problems) and thereby increase germane cognition (schema acquisition and automation).
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- Date Issued: 2013
The effect of 14 weeks of strength training on insulin resistance
- Authors: Cairncross, Joy Claudia
- Date: 2013
- Subjects: Insulin resistance , Diabetes -- Exercise therapy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10104 , http://hdl.handle.net/10948/d1018276
- Description: Insulin resistance is a precursor to type II diabetes mellitus and in conjunction with dyslipidaemia, hypertension, and obesity, these abnormalities constitute the metabolic syndrome. Insulin resistance usually develops before these other diseases and therefore identifying and successfully treating insulin resistant patients may have potentially great preventive value. Insulin resistance, obesity, and subsequently type II diabetes mellitus have increased dramatically and have reached epidemic proportions. The incidence of diabetes, and in particular type II diabetes mellitus, is increasing in developing countries and throughout the world and this is mainly as a result of increasingly sedentary lifestyle and obesity in an aging population. The specific aim of this study was to explore and describe the effect of a 14-week strength-based resistance training programme on insulin resistance amongst individuals aged 25 to 68 years, who are pre-diabetic, have T2DM, and/or are overweight. The research approach used in this investigation was explorative, experimental, and quantitative in nature. The quasi-experimental design consisted of a pre-test and post-test for an experimental and comparison group who were chosen through convenience and snowball sampling. A total of 30 participants were involved in this study, 15 participants in each group. The following dependent variables were selected, namely: body weight; BMI; body composition; waist-to-hip ratio; total cholesterol levels; triglyceride levels; HOMA-IR; and muscle strength for upper and lower body. Pre-and post-test analysis was performed at the Biokinetics and Sport Science Unit, located at the Nelson Mandela Metropolitan University (NMMU). Blood samples of the participants were drawn by nurses at the Health Clinic at the Nelson Mandela Metropolitan University and these blood plasma samples were stored at the Department of Microbiology and Biochemistry at NMMU for later analysis of glucose and insulin. The experimental group trained three times per week for a period of fourteen weeks, performing strength training exercises with progressive increments in the intensity of the exercise. The control group remained sedentary throughout the intervention period. Analysis of the data was conducted utilizing descriptive and inferential statistics. Analysis of variance (ANOVA) was used as a hypothesis-testing procedure to evaluate the mean differences. The following dependent variables showed a decrease in mean values: body weight, body mass index, body fat percentage, waist minimum, cholesterol and insulin. However these differences in results were not practically and statistically significant. The following dependent variables showed an increase in mean values: hip maximum, arm relaxed, arm flexed, thigh circumference, glucose and HOMA-IR. However these results were not practically and statistically significant. The mean differences in the plasma insulin level, pre- to post-test, between both groups indicated that a significant difference (t = -1.77, p = 0.044) existed between them. Cohen‟s d revealed a value of 0.64, which indicates moderate practical significance. The only dependent variable which showed both statistical and practical significance was sum of skinfolds. The findings for sum of skinfolds revealed that the mean differences, from pre- to post-test, between both groups indicated that a significant difference (t = -2.30, p = 0.015) existed between them. Cohen‟s d revealed a value of 0.84, which indicated a large practical significance. Although the sample size was too small to indicate generalisations to the diabetic population as a whole, strength training should be furthermore explored as an alternative and successful modality in the existing range of options available to the health and exercise professional to address the needs of the person with T2DM. The researcher proposed that a bigger sample size be used for the experimental and control group, the intervention period increased as well as various differences related to frequency, intensity and duration of strength training could possibly result in significant changes.
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- Date Issued: 2013