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Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [202]-206).

Thesis--University of Washington. / Vita. Another copy has number: Thesis 27576. Bibliography: leaves [188]-193.

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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, February 2013. / This case study supports the National Department of Education’s (DoE) strategy of integrating information and communication technologies (ICTs) into the curriculum delivery in all South African schools to enhance teaching and learning. It examined the influence of a Mindset’s multimedia digital versatile disk (DVD) instruction of chemical systems core knowledge area, a section in the grade 11 Physical Science curriculum. The main emphasis was directed at examining the influence that the DVD material would have on learners’ understanding of scientific processes and concepts in that particular section. Secondary to this objective, it looked at the attitudes and perceptions of learners and their teacher towards the classroom integration of the DVD material, also taking note of the challenges and benefits attributed to the integration itself. This study was based on the distributive cognition framework which has its roots in the socio-cultural and situated learning theories. The framework suggests that the learning process of the scientific concepts by learners is situated in a social learning environment, where learning is mediated by technological tools and artifacts (Valanides & Angeli, 2008). Under this cognitive theory the learner is positioned at the centre of the learning environment that is formulated by other people (i.e. other learners, the teacher and the community), the learning material (i.e. the content) and learning resources (i.e. physical and technological tools).Learning therefore is regarded as a social process where other people and the learning resources actively interact (Hollan, Hutchkins & Kirsh, 2000). Through the DVD’s visuals and explanations, the artificial mining environment was brought into the classroom enabling learners to be exposed to the scientific processes involved in the mining industry as a social real world activity which learners could associate with. That on its own could enhance the comprehension of content. A quasi experimental design was adopted with two grade 11 Physical Science classes from the same school, one used as an experimental group and the other one as a control group. The study sample consisted of 56 learners, 24 in the control group and 32 in the experimental group. Both classes were taught the same content by the same teacher without using the DVD lessons for a period of three weeks. Thereafter, the experimental group was exposed to the multimedia-supported lessons for three more weeks (i.e. the teacher used the DVD lessons to supplement his traditional teaching methods) while during the same period the control group was taught the same content for the same duration using the traditional teaching methods only. The pre-test and post-test measures were administered on both groups using the same instruments in order to check if the difference in the teaching approach had a positive impact or not. In addition, the data was collected in the form of questionnaires and interviews for attitudes and perceptions about using the DVD material for teaching and learning. The null hypothesis tested was: “the mean result of the experimental group would be the same or lower than that of the control group”. The t-test results showed that there was no statistical difference between the performances of the two groups hence upholding the null hypothesis. Descriptively, the results showed that learners regarded a multimedia-supported learning environment as an exciting one. They mentioned that it posed more benefits than challenges. The teacher also displayed positive attitude and perceptions about using the DVD material for teaching and learning as he indicated that it is a useful teaching tool.

Boltzmann's equation for binary chemical reactions has been solved by the modified moment method using the equivalent of the 13-moment approximations. It was found that the transport coefficients are nonlinear in the thermodynamic forces. This nonlinearity is at least quadratic. The rate coefficient also appears to be at least quadratic in fluxes. / The stability of the solutions of two coupled equations of change for the current under the influence of an electric field is examined. These equations are deduced from the structure of dissipative terms calculated in the modified moment method. Two steady state branches in current are found to bifurcate from the primary steady state branch as a critical field value E(,c) = 4.35 V/cm is crossed. The results are in good qualitative agreement with experiment. / The dynamical behaviour of the two coupled equations used above was also studied in order to establish the influence (if any) of the entropy production surface on the trajectory followed by the system. This aspect of the study proved to be difficult since the entropy production surface associated with the two equations used did not have sufficiently distinctive features. / In order to continue studies on the relationship between dynamical behaviour and the topography of the entropy production surface, the two basic equations used before were slightly modified, and new parameters were introduced. At the critical field value E(,c) = 1.48 V/cm, no secondary steady states bifurcated out of the unstable primary steady state as in the previous model. Rather, stable oscillations in current of more or less constant amplitude occurred. This may account for some of the current fluctuations observed in experiment. The entropy production surface associated with this pair of model equations consists of two intersecting locii of minima. It turns out that the trajectory follows these minimal regions for most of the orbit, crossing from one locus of minima to another either through the intersection near to the origin or by crossing a ridge of high entropy production. The average energy dissipated over this cycle turns out to be smaller than if the system had remained with the unstable steady state. / Out of the latter studies, the useful conjecture was made. Given the topography of the entropy production surface and the stability of the steady states, it is possible to qualitatively predict the dynamics of the system provided the entropy production surface has sufficiently distinctive features.

This thesis is concerned with the formation and nature of intravesicular solids in chemical and biological systems. The precipitation of Ag₂O within unilamellar vesicle microvolumes is described in detail. Formation of small (<10nm) single-domain cubic Ag₂O crystallites occurs on membrane diffusion of hydroxide ions. Nucleation initiates at a single site on the inner membrane surface followed by slow crystal growth. No precipitation is observed below an extravesicular pH (pH_OUT) of <u>ca</u>. 11.0. Permeable intravesicular nitrate ions permit hydroxide influx only when a critical membrane potential gradient is surpassed. Above a pH_OUT of 11.0 rate of precipitation is dependent on the rate of crystal growth. Kinetics are firstorder with respect to intravesicular Ag(I) concentration and approximately first-order with respect to hydroxide concentration below a pH_OUT of 12.0. Solubility equilibria for intra-and extravesicular Ag₂O formation are the same. Further <u>in situ</u> intravesicular precipitation reactions are described for FeO(OH) (crystalline), FeO(OH) (amorphous), Ag₂SiO₃ (crystalline), CoSiO₃ (amorphous), Co(OH)₂ (amorphous), Ag₂S (crystalline), CoS (amorphous), and Agl (crystalline). Precipitation of single oxidation state compounds is the same in vesicle space as for normal aqueous solution. For a mixed valency state solid, Fe₃0₄, intravesicular precipitation results in an amorphous material compared with a crystalline material prepared in aqueous solution. Inclusion of pre-formed Fe₃0₄, into vesicles is of potential use as a magnetic drug carrier system and n.m.r. relaxation probe. Intravesicular silica deposition in <u>Stephenaoeca diplocostata</u> Ellis is investigated. Siliceous costal strips are found to be extremely amorphous in structure, have surfaces active to Co(II) and Fe(III) ions, and demineralise from their centre of axis. T-joins of costal strips in intact loricae are found to be joined by a connective material containing amorphous silica centred around a filamentous material of unknown composition. Sectioned material indicates that silicification possibly initiates on an organic preformer laid down within an elongated intracellular vesicle. Potential EM stains, K₅SiPhGeW₁₁0₃₉, Gd(fod)₃, and t-BuNH₃[(nC₂₂H₄₅PO₃)₂Mo₅O₁₅] interact with vesicle bilayers resulting in observable images in the EM. Binding of K₅SiPhGeW₁₁0₃₉ can be followed by ¹H n.m.r. spectroscopy . Gd(fod)₃ loaded vesicles are potential n.m.r. probes for protein - membrane binding studies.

Thesis (Ph.D.)--University of Tulsa, 1988. / Bibliography: leaves 149-154.

The synthesis of bromochloromethane (BCM) in a batch reactor, using phase transfer catalysis, was investigated. During the synthetic procedure, sodium bromide (100.0g, 0.97mol) along with an excess amount of dichloromethane (265.0g, 3.12 mol) was charged to a reactor containing benzyl triethylammonium chloride (13 mmol), dissolved in 50 ml of water. The bench scale reactions were all carried out in a Parr 4520 bench top pressure reactor coupled to a Parr 4841 temperature controller. The method produced a 50.0 percent yield of the product BCM after a reaction time of 12 to 13 hours. The main objective for this investigation was to optimize the abovementioned reaction with respect to yield and reactor throughput. Quantitative analysis of BCM was performed on a Focus Gas Chromatograph, fitted with a flame ionization detector, and a BP20 column (30m × 0,32mm ID × 0,25 mm). Delta software, version 5.0, was applied for data collection and processing. The injector and detector port were set at 250°C and 280°C, respectively. The oven temperature was set and held at 40°C for a period of 2 minutes, then gradually increased at a rate of 10°C/min to 130°C, with the final hold time set for 1 minute. An analytical method for the quantitative analysis of BCM was developed, optimized and validated. Validation of the analytical method commenced over a period of three days, and focussed the following validation parameters: Accuracy, precision, and ruggedness. Statistical evaluation of the results obtained for precision showed that the error between individual injections is less than 2 percent for each component. However, ANOVA analysis showed a significant difference between the mean response factors obtained in the three day period (p-value < 0.05). Thus we could conclude that the response factors had to be determined on each day before quantitatively analyzing samples. The accuracy of the analytical method was assessed by using the percent recovery method. Results obtained showed that a mean percent recovery of 100.18 percent was obtained for BCM, with the absolute bias = 0.0004, and the percent bias = 0.18 percent. Hence the 95 confidence intervals for the percent recovery and percent bias are given by: (Lz, Uz) = (100.56 percent percent 102.15 percent), 13 (LPB, UPB) = (0.56 percent, 2.15 percent), respectively. Since the 95 percent confidence interval for the percent recovery contains 100, or equivalently, the 95 percent confidence interval for percent bias contains 0, the assay method is considered accurate and validated for BCM. In the same manner the accuracy and percent recovery for DCM and DBM was evaluated. The method was found to be accurate and validated for DBM, however, slightly biased in determining the recovered amount of DCM. With the analytical method validated, the batch production process could be evaluated. A total of six process variables, namely reaction time, water amount, temperature, volume of the two phases, stirring rate, and catalyst concentration, were selected for the study. The effects of the individual variables were determined in the classical manner, by varying only the one of interest while keeping all others constant. The experimental data generated was fit to a quadratic response surface model. The profile plots that were obtained from this model allowed a visual representation of the effect of the six variables. The experimental results obtained showed that the reaction follows pseudo zero-order kinetics and that the rate of the reaction is directly proportional to the concentration of the catalyst. The reaction obeys the Arrhenius equation, and the relatively high activation energy of 87kJ.mol -1 signifies that the rate constant is strongly dependent on the temperature of the reaction. The results also showed that the formation of BCM is favoured by an increase in the reaction temperature, catalyst concentration, and a high organic: aqueous phase ratio. Thus the synthesis of BCM using phase transfer catalyst could be optimised, to obtain a 100 percent yield BCM, by increasing both the reaction temperature to 105°C, and the concentration of the phase transfer catalyst -benzyl triethylammonium chloride - to 5.36 mol percent. The reaction time was also reduced to 6 hours.

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