Bachelor of Science

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  • Publication
    Validation of the 1600-m run as a predictor of VO2MAX in Singapore children aged 10 to 12 years
    Aw Yong, Wai Leng
    The purpose of the present study was to determine the validities of the 1600-m run and several anthropometric variables for predicting maximal oxygen uptake (VO2max) in Singapore children aged 10-12 years. Fourteen untrained subjects, 12 boys and 2 girls, performed the 1600-m run on a synthetic track and had VO2max determined in the laboratory. A weak correlation of -0.398 (p > 0.10) was found between VO2max and the 1600-m run time. In fact, subscapular thickness alone has the highest correlation coefficient with VO2max in this group (r = -0.863, p < 0.001). Multiple regression analysis (best-subsets) was conducted and the best predictor variables were height, weight, triceps thickness, subscapular thickness and suprailiac thickness resulting in two prediction equations: (1) VO2max ( = 79.9 - 16.6 (height, m) - 0.443 (triceps thickness, mm) -0.902 (subscapular thickness, mm)+ -0.358 (suprailiac thickness, mm), with R2 = 0.864, SEE= 2.189 (p < 0.05). and (2) VO2max (ml.ki1.min-1) = 61.8 - 0.212 (weight, kg) -0.425 (triceps thickness, mm) -0.667 (subscapular thickness, mm) + 0.315 (suprailiac thickness, mm) with R2 = 0.857, SEE = 2.248 (p < 0.05). This study thus suggests that three skinfold sites (triceps, subscapular and suprailiac), height and weight are better predictors ofVO2max than the 1600-m run.
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  • Publication
    Determination of trace metals in water by Zeeman Graphite AAS after cloud point extraction
    Xu, Huimin
    This thesis is a follow up of the research on Determination of Trace Metals in Water Samples By Atomic Spectrometry Using Cloud Point Extraction (Jianrong Chen, 2002). The academic exercise concerns the application of the preconcentration technique in separation of trace metals present in water samples. The technique applied in the study is Cloud Point Extraction (CPE). This was followed by the quantitative determination of the trace metals by using Zeeman Graphite Furnace Atomic Absorption Spectrometer (GFAAS). The metal ions of interest in the study were nickel and cobalt.

    Cloud Point Extraction works on the fundamentals of conventional liquid-liquid extraction (LLE). It is a technique that uses a non-ionic surfactant as an extractant so that trace metals can be extracted from a larger volume of aqueous phase to a much smaller volume of surfactant phase. The concentration of the surfactant must be at Critical Micellar Concentration (c.m.c) so that micelles can be formed to solubilised the trace metal in the form of metal complexes. 0.05% of Triton X-1 14 was the surfactant used. The metal complexes were formed from the reaction of chelating agent (l-2-thiazolylazo-2-naphthol; TAN at 20 μmolll) with the metal ions. This was an equilibrium reaction which was pH sensitive. The pH was maintained at 7 with phosphate buffer. When higher temperature (42 'C) was applied, the surfactant phase containing the trace metals was separated from the aqueous phase. This temperature was known as the Cloud Point (CP). This stage was facilitated by centrifugation, where small volume of surfactant phase will settle to the bottom. Estimation of chelating affinity of TAN with nickel and cobalt was also conducted. It was found that TAN had an equal affinity for both ions at pH 7.

    The resultant surfactant phase was very viscous and could not be injected into the furnace for further analyses. Thus, the viscosity was being reduced by the addition of acidified methanol. Further dilution was done by the addition of 2% (vlv) nitric acid to preserve the trace metals in the surfactant phase. This also reduced the volatility of the surfactant phase so that analytes will not be lost when waiting to be analysed on the auto-sampler plate. The furnace programme was optimised to match the analyses of the samples. Suitable pyrolysis and atomisation temperatures were chosen to give the best signal. The optimal pyrolysis temperatures were 1100°C and 1300°C for nickel and cobalt respectively. An atomisation temperature of 2300°C was used for both ions during atomisation. Sensitivity checks were conducted on both ions so as to check reliability of the instrument.

    Concentration factor, taken to be the ratio of the volume of aqueous phase over that of surfactant phase was found to fall within the range of 57 to 80 for both nickel and cobalt. Enhancement factor, which was taken as the slope of the plot of concentration of ions before CPE and after CPE had been determined. Enhancement factors of 50.6 and 57 were obtained for nickel and cobalt respectively.

    The validity of the method had been tested by conducting interference and spiked recovery tests. Over 80% of recovery had been achieved, which proved that CPE is valid as a preconcentration and separation method. Tap, pond and seawater samples were also subjected to CPE and further analysed by GFAAS for quantitative analyses.
      205  23
  • Publication
    Investigations on the synthesis of molecular rectangles based on rhenium
    Wong, Li Peng
    In this study, a series of rhenium (I) carbonyl complexes bridged by bis(bidentate) ligands (dithiooxalate, tetrathiooxalate, and dithiooxamide) were synthesised. These complexes were then reacted with linear, rigid, bifunctional N-donor ligands (4,4'- bipyridine, and pyrazine), with the aim of producing rectangular metallacycles through molecular self-assembly.

    The complex [{Re(CO)5}2(μ,ŋ1: ŋ1-C2S2O2)]was thermally decarbonylated to give [{Re(CO)3}2(μ,ŋ2: ŋ2-C2S2O2]n, which was reacted with an equivalent amount of 4,4'-bipyridine (bpy) and pyrazine (pyz), respectively. The infiared and 'H-NMR spectroscopic data of the products were consistent with them being [{Re(CO)3}2(μ,ŋ1: ŋ1-bpy)((μ,ŋ2: ŋ2-C2S2O2]n and [{Re(CO)3}2(μ,ŋ1: ŋ1-pyz)((μ,ŋ2: ŋ2-C2S2O2]n respectively, i.e. they could either be macrocycles or linear polymers, and electrospray mass spectrometric (ESMS) measurements provided strong evidence for the formation of rectangles.

    The dithiooxamidate-bridged rhenium carbonyl intermediate was prepared and reacted in analogous fashion with 4,4'-bipyridine to give a product that could be formulated, based on infrared, 1H-NMR and ESMS data, as [{Re(CO)3}2(μ,ŋ1: ŋ1-bpy)((μ,ŋ2: ŋ2-C2S2O2]2.

    Reactions involving the tetrathiooxalate-bridged rhenium carbonyl intermediate with either 4,4'-bipyridine or pyrazine consistently gave complex mixtures, as indicated by their 'H-NMR spectra. The product mixture obtained from the reaction of tetrathiooxalate-bridged rhenium carbonyl complex with 4,4'-bipyridine could include, based on infrared, 'H-NMR and ESMS data, [{Re(CO)3}2(μ,ŋ1: ŋ1-bpy)((μ,ŋ2: ŋ2-C2S4]2.
      194  30
  • Publication
    Socialisation in physical education teaching : Singapore life history investigations
    Tang, Bee Hong
    This study explored the dialectical interactions of five beginning female physical educators' 'biographical baggage' and their workplace conditions on the development of their teaching perspectives. In addition, social strategies employed by the teachers to fit into their workplace were examined. Drawing on data from a life history approach, the life histories shed light not only on the teachers' personal stories but also placed them against their social and historical context.

    The analysis of the five case studies revealed a continuum. At one extreme, lies a teacher who cruised through her induction with positive workplace conditions. At the other extreme, lies another teacher who survived by her well-established teaching perspectives in a school where her workplace conditions were trying. The other three teachers span the continuum with weaker teaching perspectives; they felt overrun by bureaucratic incursions that depleted their passion in teaching.

    Findings indicated that the PE teachers were actively involved in the creation of meanings and were not passive recipients of socialising forces at school. Findings also indicated that PETE has significantly influenced the teachers' beliefs about teaching PE. This is in contrast with previous studies that reported PETE had little influence on teachers' teaching perspectives. However, many teachers in this study found the cultural code of PE as a subject marginalised too powerfully for them to address with their imbued teaching perspectives. Hence, many suffered a similar plight as other teachers in previous research in terms of reality shock, isolation, role conflict, and wash-out effect.

    The present study reaffirmed Wright's (2001) findings that beginning Singaporean PE teachers were uninterested in a custodial approach to teaching PE and they did not prefer coaching to teaching. These are in contrary to previous findings from western countries. In line with the literature, the findings suggested that schools provide inadequate support for beginning teachers. The study suggests how a comprehensive mentorship programme may help beginning PE teachers thrive in the 'real world' of teaching.
      206  46
  • Publication
    Development of X-pinch with a 200 kV pulse transformer power supply
    Tan, Lay Koon
    The objective of this project is to develop a first ever X-pinch at the National Institute of Education - Natural Sciences Academic Group - Plasma radiation source Laboratory with major emphasis on the designing of a High Voltage Pulse Power Supply system for it.

    A High Voltage Power Supply (HVPS) that charge a Pulse Forming Line (PFL) was designed, constructed and characterized. The HVPS system consists of several stages to produce finally an extremely high voltage - 200kV in time duration of approximately 2 ps. An ultra fast high voltage capacitive voltage probe was also developed for testing of this HVPS. This capacitive probe was used in the initial testing of the HVPS as commercial voltage probes are usually not rated above 40kV.

    The final product is an X-pinch which was characterized for its electrical, x-ray emission and plasma dynamics properties using various probes like V-dot, Rogowski groove, Photo Conducting Diamond (PCD), and photographic films. X-pinch plasma was generated by passing a 16 kA current through a two 5pm tungsten wire or two 1Spm gold wire. The plasma from the X-pinch was also being investigated using time integrated optical photography which revealed that there is a bright region at the X-point. Plasma was found to extend axially above and below the X-pinch. In addition, diffused and non-uniform plasma was found to extend from1 the wires forming the pinch. Evidence for the production of the Ultraviolet was also seen using Photo Conducting Diamond (PCD) detectors.
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