No description available.

The objective of the research presented in this thesis was to investigate the effects of wearout processes on the performance and reliability of CMOS bistable circuits. The main wearout process affecting reliability of submicron MOS devices was identified as hot-carrier stress (and the resulting degradation in circuit performance). The effect of hot-carrier degradation on the resolving time leading to metastability of the bistable circuits also have been investigated. Hot-carrier degradation was identified as a major reliability concern for CMOS bistable circuits designed using submicron technologies. The major hot-carrier effects are the impact ionisation of hot- carriers in the channel of a MOS device and the resulting substrate current and gate current generation. The substrate current has been used as the monitor for the hot-carrier stress and have developed a substrate current model based on existing models that have been extended to incorporate additional effects for submicron devices. The optimisation of the substrate current model led to the development of degradation and life-time models. These are presented in the thesis. A number of bistable circuits designed using 0.7 micron CMOS technology design rules were selected for the substrate current model analysis. The circuits were simulated using a set of optimised SPICE model parameters and the stress factors on each device was evaluated using the substrate current model implemented as a post processor to the SPICE simulation. Model parameters for each device in the bistable were degraded according to the stress experienced and simulated again to determine the degradation in characteristic timing parameters for a predetermined stress period. A comparative study of the effect of degradation on characteristic timing parameters for a number of latch circuits was carried out. The life-times of the bistables were determined using the life-time model. The bistable circuits were found to enter a metastable state under critical timing conditions. The effect of hot-carrier stress induced degradation on the metastable state operation of the bistables were analysed. Based on the analysis of the hot-carrier degradation effects on the latch circuits, techniques are suggested to reduce hot-carrier stress and to improve circuit life-time. Modifications for improving hot- carrier reliability were incorporated into all the bistable circuits which were re-simulated to determine the improvement in life-time and reliability of the circuits under hot-carrier stress. The improved circuits were degraded based on the new stress factors and the degradation effects on the critical timing parameters evaluated and these were compared with those before the modifications. The improvements in the life-time and the reliability of the selected bistable circuits were quantified. It has been demonstrated that the hot-carrier reliability for all the selected bistable circuits can be improved by design techniques to reduce the stress on identified critically stressed devices.

Thesis (Ph.D.(Environmental Economics)) -- University of Pretoria, 2007. / Includes bibliographical references.

Thesis (M.S.)--Michigan State University. Civil Engineering, 2008. / Title from PDF t.p. (Proquest, viewed on Aug. 11, 2009) Includes bibliographical references (p. 78-82).

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis (Ph. D.)--State University of New York at Binghamton, Philosophy Department (Philosophy, Interpretation and Culture Program), 2005. / Includes bibliographical references.

Comparisons were made between the sensitivities of unique ‘wild’ isolates and domestic isolates of the dry rot fungus, <i>Serpula lacrymans</i>, to temperature, water potential and pH. Comparisons were also made between their capacities of timber decay. The ‘wild’ Himalayan isolates displayed slightly less marked sensitivities to high and low temperature and lowered water potential, yet the isolates were equally tolerant of pH. In general, the linear growth rates of the domestic isolates proved to be twice those of the ‘wild’ Himalayan set, whereas little variation occurred between their rates of timber decay. This study also resulted in the first isolation and reliable identification of ‘wild-growing’ <i>S. lacrymans</i> collected in Europe. The main part of the project involved the construction of novel chambers in order to examine the effects of lowered humidity and moving air flow on the activity of <i>S. lacrymans</i>. In the smallest and simplest of these, its growth and timberdecaying activities could be stopped by incubation at 86% relative humidity or by the application of a pumped air flow rate of 2.5 litres per minute; however, <i>S. lacrymans</i> was not inactivated until more-stressful conditions were applied. In addition, an intermediate rate of air flow provoked marked directional growth away from the stress. Furthermore, the introduction of stone, brick and plaster into these models encouraged the capacities of timber decay and mycelial growth. The use of a larger and more representative model incorporating simulated flooring and plaster walling within glass tanks revealed differences in the appearances and patterns of colonisation by <i>S. lacrymans</i> depending upon whether aged or new materials were used. Treatments involving air drying by fans caused both a shrivelling and a loss of viability of the fungus only when there was no ‘reservoir’ of water available; when there was water present, latent activity remained. An elaboration of this experimental design tested the effects of a combined biological and environmental treatment. Subsequently, the application of <i>Trichoderma harzianum</i>, a known antagonist of <i>S. lacrymans</i>, proved not to be an effective remedial treatment on its own, but appeared to impart a mildly protective effect when combined with a drying regime. Importantly, in the latter situation <i>T. harzianum</i> caused a severe degradation of the part of the colony responsible for the uptake of water in <i>S. lacrymans</i>. Another workshop-scale model simulating more authentically a damp sub-floor space and a cavity behind aged plaster walling was developed. When respective treatments by fan drying and passive ventilation were compared, the former were more effective, but its efficacy could be augmented by incorporating low-level passive ventilation via discreet vents. In this manner, a successful remedial treatment of <i>S. lacrymans</i> could be effected, though the prevalence of mould could prove to be undesirable in practice. However, some samples of this displayed antagonistic effects against <i>S. lacrymans</i>. A further experiment was designed to test the effects of air drying on the production of the stress-protective carbohydrate trehalose and of some associated solutes by <i>S. lacrymans</i>. In contrast to reports of some other organisms, no definite stockpiling of any of the compounds occurred. A final series of experiments revealed that <i>S. lacrymans</i> removed calcium, silicon and iron from sandstone and calcium, sulphur and iron from aged plaster; these elements were sequestered on its hyphae, especially in the form of calcium oxalate. Degradation of the sandstone was implicit but not obvious microscopically. Furthermore, <i>S. lacrymans</i> transported iron from these building materials through its mycelial system. An attempt to determine the effects of separate minerals in sandstone and plaster on timber decay revealed few variations.

No description available.

The work described in this thesis attempts to analyse the accumulation and degradation of cytochrome P-450 in Saccharomyces cerevisiae. The effect of environmental parameters such as oxygen and constituents of the growth medium have been examined here in an attempt to understand the mechanism underlying the accumulation and degradation of this enzyme. The highest level of S. cerevisiae cytochrome P-450 accumulation was recorded with a new strain NCYC 754 obtained from NCYC 240 and first investigated here. Cytochrome P-450 was found to accumulate during growth of S. cerevisiae only at high glucose concentrations under conditions of mitochondrial repression. It was found that in non-growing yeast a 100 ml 8% glucose (w/v) solution would enhance cytochrome P-450 accumulation. Scale-up of this effect in a 5 l bioreactor was attempted. In experiments on the removal of oxygen during the exponential growth of S. cerevisiae there was found to be a decline in cytochrome P-450 accumulation in which case it is suggested that oxygen may be acting as a substrate inducer of yeast cytochrome P-450. Culture shake speed was also used to control oxygen availability. An optimum shake speed was found which allowed the greatest rate of cytochrome P-450 accumulation, it was also found that the same shake speed caused the greatest rate of degradation of the enzyme during stationary phase. It was also discovered that semi-anaerobic conditions caused less degradation than aerobic conditions. The agents chloramphenicol, dinitrophenol and cycloheximide offered less protection against degradation than semi-anaerobic conditions. Ethanol was found to induce cytochrome P-450 in S. cerevisiae under conditions where cytochrome P-450 is not normally detectable. Added alkanols, other than ethanol, cause rapid degradation of cytochrome P-450 in non-growing yeast.

Orientador: Maria Valnice Boldrin Zanoni / Banca: Paulo Roberto Bueno / Banca: Arthur de Jesus Motheo / Banca: Romeu Cardozo Rocha Filho / Bana: Rodnei Bertazolli / Resumo: O comportamento eletroquímico de três corantes dispersos, Vermelho Disperso 1, Laranja Disperso 1 e Vermelho Disperso 13 foi investigado em N,N-dimetilformamida usando tetrafluorborato de tetrabutilamônio como eletrólito de suporte. O grupo nitro dos corantes é reduzido em potenciais de -0,85 V, -0,79 V e -0,69 V, respectivamente, para os corantes Vermelho Disperso 1, Laranja Disperso 1 e Vermelho Disperso 13. A oxidação do grupo amino, também presente nos corantes investigados, ocorre, respectivamente, em potencial de 0,95 V, 0,90 V e 1,0 V e promove a clivagem do grupo azo. Devido à toxicidade e mutagenicidade destes corantes, analisada pelos testes de citotoxicidade em células humanas embrionárias HEK293 e de Ames, respectivamente, investigou-se no presente trabalho novos métodos de degradação dos mesmos em meio aquoso usando o agente dispersante comercial "Emulsogen" por meio de tratamento com cloro ativo (cloração convencional) e fotoeletroquimicamente pela geração de radicais cloro "in situ" sobre eletrodos nanoparticulados de Ti/TiO2, preparados pelo método sol-gel, em NaCl 0,1 mol L-1. A oxidação fotoeletrocatalítica, sobre eletrodos nanoparticulados de Ti/TiO2 em NaCl, mostrou-se mais eficiente quando comparada à cloração convencional, tanto na descoloração que promoveu 100% de remoção de cor, quanto na mineralização dos mesmos (até 60% de remoção de COT). A mutagenicidade dos corantes estudados foi drasticamente reduzida após tratamento fotoeletroquímico. No entanto, a cloração convencional não foi eficiente para total remoção da atividade mutagênica dos corantes, observando-se, ainda, um aumento para o corante Vermelho Disperso 13. A degradação também foi investigada sobre eletrodos de nanotubos de Ti/TiO2, preparados pelo método de anodização eletroquímica... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The electrochemical behavior of three disperse dyes, Disperse Red 1, Disperse Orange 1 and Disperse Red 13, was investigated using N,N-dimethylformamide using in tetrabutylammonium tetrafluoroborate as supporting electrolyte. The nitro group of the dyes is reduced in potential of -0.85 V, 0.79 V and -0.69 V, respectively, for Disperse Red 1, Disperse Orange 1 and Disperse Red 13. The oxidation of amine group, also presents in the dyes molecules, occurs, respectively, at 0.95 V, 0.90 V and 1.0 V and promotes cleavage of azo group. Because of these dyes toxicity and mutagenicity, analyzed by citotoxicity in embryonic human cells HEK293 and mutagenicity detected by Ames test, respectively, new methods of degradation of these dyes in aqueous medium using the commercial dispersant agent "Emulsogen" was investigated by active chlorine treatment (conventional chlorination) and photoelectrochemically by "in situ" chlorine radicals generation using Ti/TiO2 nanoparticulates electrodes, prepared by solgel method, in 0.1 mol L-1 NaCl. The photoelectrocatalytic oxidation, using Ti/TiO2 nanoparticulates electrodes in NaCl presented higher efficiency when compared to conventional chlorination, leading to 100% of color removal and also 60% of mineralization of dyes measured as TOC removal. The mutagenicity of all investigated dyes was dramatically reduced after photoelectrochemical treatment. However, the conventional chlorination was not efficient for mutagenic activity removal of dyes and promoted an increase for Disperse Red 13. The degradation was also investigated using Ti/TiO2 nanotubes electrodes, prepared by electrochemical anodization in fluoride medium and characterized by SEM and photocurrent curves. These electrodes presented 100% of discoloration of all investigated dyes and total organic carbon removal around 70% after 3 hours of photoelectrocatalytic degradation... (Complete abstract click electronic access below) / Doutor