A dissertation submitted to the Faculty of Science, University of the Witwa- tersrand, Johannesburg, in ful llment of the requirements for the degree of Master of Science. Johannesburg, 5 September 2013 / This dissertation aims to conduct a comprehensive and up to date review of reliability bounds for the binary coherent systems. We assume that the components work independently of each other. The bounds are compared numerically by using simple structures.

A place for no place is a practice based research project that investigates the notion of in-between space. The focus of this project is to consider the nature of binary oppositions and the thresholds between, through the designing of memorial space. The key issue of this project is aimed at investigation of the nature of thresholds of dualism, contrasting dualities and binary oppositions.With help of this project, I attempt to discuss a design methodology by balancing the binarization in natural environment in terms of applying their principles to creating the space, meanwhile, making the space from outside Visually the practical part of the exegesis will grow from process of spatial analysis and detailing by consulting with the key spatial binary oppositions of the site specific projects – Flat Alleyway and Wen-chuan Earthquake Memorial Park. Spatial arrangement and function, along with their codified details will be domesticated with concerns of the special character of the site and the consideration of scale, function, body movement, interior and exterior decoration aspects of the space. The result will be a cohesive range that represents new spaces by the meaning of In-Between-Ness. Heuristic and practical projects are my main methodological approaches. My work does not seek to fix a solution by the notion of in-between, but open up area of ongoing discovery. The practical spatial design projects are regarded as a process of meditation for a self-development, which allows me to reconsider, renegotiate, reflect and renew my work throughout the practical process. In this way, hidden spatial codes can be brought out to the surface.

Flammability is an important factor of safe practices for handling and storage of liquid mixtures and for the evaluation of the precise level of risk. Flash point is a major property used to determine the fire and explosion hazards of a liquid, and it is defined as the minimum temperature at which the vapor present over the liquid at equilibrium forms a flammable mixture when mixed with air. Experimental tests for the complete composition range of a mixture are time consuming, whereas a mixture flash point can be estimated using a computational method and available information. The information needed for mixture flash point predictions are flashpoints, vapor pressures, and activity coefficients as functions of temperature for each mixture component. Generally, sufficient experimental data are unavailable and other ways of determining the basic information are needed. A procedure to evaluate the flash point of binary mixtures is proposed, which provides techniques that can be used to estimate a parameter that is needed for binary mixture flash point evaluations. Minimum flash point behavior (MFPB) is exhibited when the flash point of the mixture is below the flash points of the individual components of the mixture. The identification of this behavior is critical, because a hazardous situation results from taking the lowest component flash point value as the mixture flash point. Flash point predictions were performed for 14 binary mixtures using various Gex models for the activity coefficients. Quantum chemical calculations and UNIFAC, a theoretical model that does not require experimental binary interaction parameters, are employed in the mixture flash point predictions, which are validated with experimental data. MFPB is successfully predicted using the UNIFAC model when there are insufficient vapor liquid data. The identification of inherent safety principles that can be applied to the flammability of binary liquid mixtures is also studied. The effect on the flash point values of three binary mixtures in which octane is the solute is investigated to apply the inherent safety concept.

By evaporating single element to grow two kinds of stacked layer precursors In/Cu/Se and In/Se/Cu first, In/Cu/Se precursor forms as CuSe2, CuSe and In metal phase, but In/Se/Cu precursor forms mainly as Cu11In9 alloy, In metal phase and amorphous Se. In RTA selenization process, the two kinds of stacked layer precursors form to CuInSe2 (for short as CIS) thin film in different reaction mechanisms, but both of the two stacked layers form to CIS with rough surface and uncompact structure, not the ideal thin film. Replacing by co-evaporating two elements to grow two kinds of binary stacked layrer precursors InSe/CuSe/Se and InSe/Cu/InSe/Se, finds that, after the RTA selenization process, both of the two precursors form CIS with good smoothness and compactness, and InSe/CuSe/Se precursor with much better structure than the other, having mean grain size in about 1~3£gm. In this result, appears that if skipping the stage which single element reacts with Se, generating the selenide InxSey, CuxSey (Such as InSe, In2Se3, CuSe, Cu2Se et cetera.), and using In-Se, Cu-Se binary stacked precursors in RTA process directly can acquire better CIS structure. And then, growing InSe/CuSe/Se stacked layer on Mo metal back contact, finds the phenomenon that the formed CIS thin film has many circle bulges structure on Mo thin film. After investigating this case, the reason was considered as the remaining compressive stress of Mo thin film (-272.9MPa). The interface problem of Mo/CIS has been solved by tuning the remaining stress of Mo with 1£gm thickness to compressive stress -194MPa, and 1£gm thickness CIS thin film is grown on that. However, if the remaining stress continuingly drecrese to almost no stress 1MPa or tensile stress 709.9MPa, CIS thin film peels with Mo thin film from the substrate. In the end, analyzing the CIS thin film formed by InSe/CuSe/Se stacked layer precursor (Cu/In ratio is 24%/26%), the result shows that the CIS film is a P-type In-rich thin film, the sheet resistence is 6.8*106£[/ ¡¼, carrier mobility is 1.103*102 cm2/V-s, carrier density is 1.318*1018 cm-3, and energy gap is about 1.0eV, the absorption coefficient is above 6.5*104cm-1, and the composition all over the film is very close to each other¡Aappearing this film with nice composition homogenization.

Thesis (Ph. D.)--Johns Hopkins University, 1916. / Biographical note. "Reprinted from American journal of mathematics, vol. XL, no. 2, April, 1918."

Thesis--M. Phil., University of Hong Kong, 1979.

Computer hardware and software evolve very fast. With the advent of chip-multiprocessors and symmetric multithreading, multiprocessor hardware configurations are becoming prevalent. For software, new hardware and requirements such as security, performance and maintainability drive the development of new runtime environments, virtual machines and programming methodologies. These trends present problems when porting legacy software. Multiprocessor hardware require ports of uniprocessor operating system kernels while new software environments might require that programs have to be ported to different languages. This thesis examines the tradeoff between performance and development effort for software porting with case studies in operating system porting to multiprocessors and tool support for porting C and C++ applications to Java virtual machines. The thesis consists of seven papers. The first paper is a survey of existing multiprocessor development approaches and focuses on the tradeoff between performance and implementation effort. The second and third papers describe the evolution a traditional lock-based multiprocessor port, going from a serialized “giant locked” port and evolving into a coarse-grained implementation. The fourth paper instead presents an alternative porting approach which aims to minimize development effort. The fifth paper describes a tool for efficient instrumentation of programs, which can be used during the development of large software systems such as operating system kernels. The sixth and seventh papers finally describe a binary translator which translates MIPS binaries into Java bytecode to allow low-effort porting of C and C++ applications to Java virtual machines. The first main contributions of this thesis is an in-depth investigation of the techniques used when porting operating system kernels to multiprocessors, focusing on development effort and performance. The traditional approach used in the second and third papers required longer development time than expected, and the alternative approach in the fourth paper can therefore be preferable in some cases. The second main contribution is the development of a binary translator that targets portability of C and C++ applications to J2ME devices. The last two papers show that the approach is functional and has good enough performance to be feasible in real-life situations.

published_or_final_version / Mathematics / Master / Master of Philosophy

published_or_final_version / Mathematics / Master / Master of Philosophy

This thesis is an investigation of the binary toxin of Clostridium difficile. The aim was to improve the understanding of the role of the binary toxin in pathogenesis. Quantitative real-time PCR (qPCR) was used to study expression of cdtA encoding the binary toxin enzymatic domain, cdtR encoding the binary toxin regulator and tcdB encoding toxin B, in response to growth phase and antimicrobial treatments in 2 C. difficile strains. Validation of a set of stable reference genes was required prior to qPCR analysis of gene expression. A universal set of genes could not be identified and reference genes should be validated on a strain-specific basis. Significant increases or decreases in expression were observed in response to levofloxacin and enrofloxacin exposure. The 2 strains selected were from different ribotypes and did not always share expression patterns. Binary toxin loci were sequenced in and compared between 10 C. difficile strains. A non-sense mutation in the cdtR gene of a ribotype 078 strain was identified and found to be restricted to toxinotype V isolates. This mutation is predicted to result in a truncated, non-functional protein. Despite the mutation, cdtA expression was still detected by qPCR. Finally, an evaluation of commercial nucleic acid extraction kits was performed. All kits produced RNA of adequate quality and yield, however, RNA isolated using the the Roche MagNA Pure LC RNA Isolation Kit could not be analyzed using the Agilent Bioanalyzer. It could not properly assign RNA integrity numbers due to a failure to remove small RNAs which were interpreted as degradation. All kits were suitable for DNA extraction with the exception of the MagNA Pure LC DNA Isolation Kit III which produced sheared DNA. In conclusion, this study demonstrated that the binary toxin regulator isn’t necessary for toxin expression and suggests other regulators of expression exist. Binary toxin gene expression did not necessarily correlate with expression of tcdB and expression levels vary between strains. This study also highlighted how the heterogeneity of C. difficile complicates gene expression experiments and the need for assessment of nucleic acid extraction methods due to critical variations between established commercial systems.