Current-voltage (I-V) characteristics of organic molecular glasses and solution processable materials embedded between two electrodes were studied to find materials possessing high charge-carrier mobilities and to design organic memory devices. The comparison studies between TOF, FET and SCLC measurements confirm the validity of using analyses of I-V characteristics to determine the mobility of organic semiconductors. Hexaazatrinaphthylene derivatives tri-substituted by electron withdrawing groups were characterized as potential electron transporting molecular glasses. The presence of two isomers has important implications for film morphology and effective mobility. The statistical isomer mixture of hexaazatrinaphthylene derivatized with pentafluoro-phenylmethyl ester is able to form amorphous films, and electron mobilities with the range of 10 E cm2/Vs are observed in their I-V characteristics. Single-layer organic memory devices consisting of a polymer layer embedded between an Al electrode and ITO modified with Ag nanodots (Ag-NDs) prepared by a solution-based surface assembly demonstrated a potential capability as nonvolatile organic memory device with high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag-NDs that act as trapping sites, reducing the current in the OFF state. Based upon the observed electrical characteristics, the currents of the low-resistance state can be attributed to a tunneling through low-resistance pathways of metal particles originating from the metal top electrode in the organic layer and that the high-resistance state is controlled by charge trapping by the metal particles including Ag-NDs. In an alternative approach, complex films of AgNO3: hexaazatrinaphthylene derivatives were studied as the active layers for all-solution processed and air-stable organic memory devices. Rewritable memory effects were observed in the devices comprised of a thin polymer dielectric layer deposited on the bottom electrode, the complex film, and a conducting polymer film as the top electrode. The electrical characteristics indicate that the accumulation of Ag+ ions at the interface of the complex film and the top electrode may contribute to the switching effect.

This study highlighted the implications of the absence of well-delineated criteria for the workplace-effective mobility of employees with disabilities in South Africa for their employment, development and organisational mobility. In response to the dearth of research on workplace-effective mobility, and cognizant of the importance of well-delineated workplace criteria to oppose continuing workplace prejudice and discrimination against employees with disabilities, this two-phase sequential triangulation study aimed to identify and confirm criteria and compile a theoretical model for workplace-effective mobility of employees with disabilities. The study has significance for the achievement of greater workplace equity and redress, which will enhance the strategic human resources management and the productive image of employees with disabilities, as well as reduce welfare costs by enabling more people with disabilities to access paid employment opportunities. To attain the study objectives, the study was done in two phases. The first was a qualitative phase during which focus group interviews with participants with disabilities were conducted. The second phase involved a five-point Likert scale-based Delphi process with industrial and organisational psychologists. Focus group participants were formally employed or self-employed in various organisations and were recruited from four disability categories (people who are blind or deaf, or have a physical or speech impairment) in four provinces in South Africa (the Free State, Gauteng, KwaZulu-Natal and the Western Cape). The industrial and organisational psychologists who participated in the Delphi phase were used as experts with prior experience in the employee recruitment area. The study found that workplace-effective mobility is (a) a multi-dimensional concept comprised of a positive self-concept, self-efficacy, workplace accessibility, a sense of coherence and a positive sense of independence, which form the crux of criteria for workplace-effective mobility; (b) a result of self-efficacy beliefs, enabling organisational practices and workplace accessibility; and (c) at the heart of the pursuit for workplace equity to redress prejudice and discrimination against employees with disabilities in the workplace. The participating experts also reached consensus in their understanding of the term workplace-effective mobility. Within-group differences were identified for a number of categories; and therefore it is recommended that future research should be conducted on distinct categories of disabilities. Using the identified dimensions (positive self-concept, self-efficacy, workplace accessibility, sense of coherence and a positive sense of independence) and outcomes (organisational and personal effectiveness), a theoretical model of workplace-effective mobility was compiled. / Thesis (PhD)--University of Pretoria, 2011. / Human Resource Management / unrestricted

Capillary electrophoresis is a widely used separation method of analytical chemistry. Addition of a selector into the background electrolyte extends its applicability to separation of enantiomers or of compounds of similar physicochemical properties. In analytical practice, mixtures of selectors are also commonly used - either prepared intentionally to achieve better separation or because commercially available selectors may be mixtures of compounds differing in the degree of substitution and substituent positions. Mathematical description of these systems, which are highly relevant in analytical practice, can simplify search for optimal separation conditions. Also, it provides a useful insight into the separation mechanism. In this work, a model of electromigration of an analyte interacting with a mixture of two selectors is proposed and experimentally verified. This model results from a more general description of systems with an arbitrary number of selectors. The model shows that a selector mixture can be treated as a single selector if the ratio of the respective selector concentrations is kept constant. When the mixture is prepared intentionally, this description predicts, how separation potential of the mixture changes with its composition. Thus it allows the optimal composition and total...