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Cellular redox homeostasis mediates a wide range of physiological and developmental processes. Various stresses trigger over-production of reactive oxygen/nitrogen species which leads to oxidative modifications of redox-sensitive proteins. Identification and characterization of redox-sensitive proteins are important steps toward understanding molecular mechanisms of stress responses. In the study, a high-throughput quantitative proteomic approach termed OxiTRAQ was developed for identifying proteins whose thiols undergo reversible oxidative modifications in Arabidopsis cells subjected to oxidative stress. In this approach, a biotinylated thiol-reactive reagent is used for differential labeling of reduced and oxidized thiols, and the biotin-tagged peptides are affinity-purified and labeled with iTRAQ reagents for quantitation. This approach allows identification of the specific redox-regulated cysteine residues in proteins and offers an effective tool for elucidation of redox proteomes. With this approach, we identified 195 cysteine-containing peptides from 179 proteins whose thiols underwent oxidative modifications in Arabidopsis cells following the treatment with hydrogen peroxide. A majority of those redox-sensitive proteins, including several transcription factors, were not identified by previous redox proteomics studies. Besides, this method was also used to identify proteins that underwent oxidative modifications in Arabidopsis cells subjected to 15 minute treatment of salicylate (a key signaling molecule in the plant defense pathway) or flg22 (a peptide from bacterial flagellin that induces pathogen associated molecular patterns-triggered immunity). In total, 127 peptides from 111 distinct proteins were identified as salicylate- and/or flg22-responsive redox-sensitive proteins. Among the identified redox sensitive proteins are many regulatory proteins including those involved in chromatin remodeling, transcription, nucleocytoplasmic shutting, and posttranslational regulation. Furthermore, in vivo 15N metabolic labeling method combined with a cysteine-containing peptide enrichment technique was applied to identify proteins that undergo oxidative modifications in plants in response to pathogen attack. The identification of redox-sensitive proteins provides a foundation from which further study can be conducted toward understanding the biological significance of redox signaling in plant stress response.

Vapour products (e-cigarettes) have rapidly grown in sales. While competing claims about the effects of vaping are fiercely debated within the public health community, no studies have examined the claims accepted in the regulatory arena. In the first article of this manuscript-based dissertation, my co-authors and I utilized narrative policy framework to identify the claims about vapour devices in legislation recommendation reports from Queensland Australia, Canada, and the European Union, and the United States. The vast majority of claims represented vapour devices as a threat, while the potential benefits were very rarely presented, resulting in bans and strict regulations. Evidence on two claims, youth vaping as a risk for nicotine dependence, and vapour products as a cessation aid, was evaluated with systematic reviews. For the youth claim, we retrieved population surveys on (1) the first product used, (2) non-nicotine vaping, (3) the prevalence of infrequent users among past-30-day users, and (4) cannabis vaping. Surveys indicated that a near majority of students who were past-30-day users vaped only once or twice a month, and an appreciable number, 25% and more, reported consuming non-nicotine liquids. Furthermore, 80% to 90% of ever-users tried cigarettes first. Far fewer youth are at a risk for nicotine addiction than indicated by any past-30-day use. On the other hand, vaping as a mode of administration of other drugs has received little attention, and presents an unknown risk to youth. We evaluated the claims about cessation with a review of systematic reviews (umbrella review). Three reviews, Hartmann-Boyce et al. (2016), Malas et al. (2016) and El-Dib et al. (2017) received the better quality ratings. They were unable to reach a definitive conclusion due to the limited number of randomized controlled trials and the low quality of most of the studies. We considered the reviewers’ tentative statements on their findings, the findings of the quality cohort studies, the potential underestimation of effectiveness in the studies, and the improved nicotine delivery of newer models. The weight of the evidence allowed us to state our optimism that vapour products have potential as a cessation aid. In the jurisdictions studied in this dissertation, vapour products have been claimed to be a threat by leading youth to smoking and impeding cessation. Does the evidence support the claims? The possible risk of youth becoming dependent on nicotine from vaping is substantially lower than indicated by the metric of any past-30-day use. There is reasonable evidence that vapour products may be an effective cessation aid. With a better understanding of these two claims, we in public health should revisit the regulations, policies, and interventions for vapour products so that they are in line with the evidence, not unsupported claims. / Graduate / 2019-04-02

Doctor of Philosophy / Department of Chemical Engineering / Peter H. Pfromm / Since its inception, the Haber-Bosch (HB) process for ammonia (NH3) synthesis has allowed for a significant increase in global food production as well as a simultaneous decrease in global hunger and malnutrition. The HB process is estimated to be responsible for the subsistence of 40% of the world population as approximately 85% of the over 182 metric tons of NH3 produced in 2017 was used as fertilizer for crop production. The natural gas consumed (mostly to generate H2) represents approximately 2% of the global energy budget, while the CO2 produced is about 2.5% of all global fossil CO2 emissions. Approximately 40% of food consumed is essentially natural gas transformed by the HB process into agricultural products. However global food production will need to double due to expected increase in world population to 9.6 billion by 2050 and rising demand for protein among developing nations. A novel thermochemical reaction cycle for sustainable NH3 synthesis at atmospheric pressure is explored herein. Both thermochemical and kinetic rationales are discussed regarding choice of Mn as the cycled reactant. The energetic driving force for these reactions is conceptually derived from concentrated solar energy. Mn was reacted with N2 forming Mn-nitride, corrosion of Mn-nitride with steam at 500 °C formed MnO and NH3, and lastly MnO was reduced at 1150 °C in a 4 vol % CH4 – 96 vol % N2 stream to Mn-nitride closing the cycle. Optimum nitridation at 800 °C and 120 min produced a Mn6N2.58-rich Mn-nitride mixture containing 8.7 ± 0.9 wt. % nitrogen. NH3 yield was limited to 0.04 after 120 min during nitride corrosion but addition of a NaOH promotor improved NH3 yield to 0.54. Mn6N2.58 yield was 0.381 ± 0.083 after MnO reduction for 30 min with CO and H2 but no CO2 detected in the product. Mn-nitridation kinetics were investigated at temperatures between 600 and 900 °C for 10 and 44 μm reactant powder particle sizes. That equilibrium conversion decreased with increasing temperature was confirmed. Jander’s rate law, which assumes gaseous reactant diffusion through a solid product layer, described the experimental data reasonably well. The rate constants and initial rates were as much as an order of magnitude greater for the 10 μm Mn reactant particle size. Additionally the activation energy was found to be 44.1 kJ mol-1 less for the 10 μm reactant particle size. Reducing the particle size had a small but positive effect on Mn-nitridation kinetics. Further reducing particle size will likely have a greater impact. A review of relevant classical thermodynamics is discussed with special attention paid to open systems. Confidence issues regarding over-reliance on x-ray diffraction are considered with options suggested for mitigation. Opportunities for future work are assessed.

Ph.D. (Computer Science) / The development of software systems is a relatively recent field of human endeavour. Even so, it has followed a steady progression of dominant paradigms which have incrementally improved the ease with which developers are able to express the logic and structure of their systems. The initially unstructured era of free-form spaghetti code gave way to structured programming in which the entry and exit points of functional units were well defined through the creation of abstractions such as procedures, sub-routines and functions. The problem of correctly associating data with the set of operations which are legal on this data was addressed through the concept of encapsulation with the onset of object-oriented programming. Object orientation also introduced a set of abstractions for safe code reuse through inheritance and dynamic polymorphism as well as composition/aggregation and delegation. The agent-oriented software development paradigm, when viewed as an extension of object orientation, adds the capacity of agent autonomy to an object, which allows it to select for itself which of its operations it will execute at any point in time. In addition, the separation between an agent and the environment within which it is embedded must be well defined. Agent autonomy allows for the modelling and development of loosely coupled systems with the capacity for complex emergent behaviour. The mapping of a given set of environmental percepts to an agent's operation selection defines its agent function and hence its emergent behaviour. Furthermore, agents may also be embedded into a shared environment together with other agents forming a multi-agent system. The emergent characteristics of such systems are defined not only through changes in environment state but also via agent to agent interactions. Multi-agent systems are categorised into cooperative or competitive based on whether all the agents within the system share a common goal. An argument is presented that even within cooperative multi-agent systems selfishness will emerge as a direct consequence of computational intractability. The core of the argument centres on the finite nature of the computational resources available to an agent which must be divided between the evaluation of the usefulness of other agent's knowledge and intentions towards improving the collective utility of the system and directly acting upon its own. As a direct result of the halting problem it is impossible for an agent to ascertain in general whether another agent's plans are even feasible (i.e. will result in the system reaching a goal state). As a direct consequence of such a limitation agents will in general favour their own courses of action over those of others and hence an emergent selfishness occurs even in ostensibly cooperative systems...

M.Tech. / The efficiency of hydrochloric acid leaching of gold from low grade gold-bearing material has been investigated in the presence of sodium hypochlorite (NaOCl) to produce in situ chlorine gas which is an oxidizing agent able to oxidize gold metal to gold soluble forms: Au+ and Au3+. The effect of concentrations of HCl, NaOCl, and mixtures HCl + NaOCl was sought. An investigation on chlorine species was conducted to predict their stability areas. The reactions involved and their mechanisms were established. Prior to leaching, the feed was subjected to fire assay, Atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) analyses, to quantify the various elements, and to find out the chemical composition and the different mineralogical phases which are present. The main minerals found in the feed were: quartz, pyrite, muscovite-2M1, (M); and clinochlore. The grade was found to be 0.62 g/t. It was found from the hydrochloric acid leaching process that most of metals constituents (iron and potassium) of the feed were leached and consumed all the hydrochloric acid. Therefore, leaching of gold from low grade gold-bearing materials in aqueous chlorine solution is not an effective process for now. Hydrochloric acid leaching of cobalt and copper from four oxidized cobalt-bearing ores was studied in the presence of FeCl2 to produce in situ Fe2+ that is a reducing agent able to reduce Co3+ to Co2+ which is the soluble form of cobalt. The effects of the concentrations of HCl, FeCl2, mixture HCl + FeCl2, leaching time, particle size, and the dissolution kinetics were investigated. Prior to leaching the feeds were characterized with XRD, XRF, FTIR, AAS, Scanning electron microscopy (SEM), and gravimetric analysis. Cobalt contents were found to be between 2.59% and 39.76% in the four ores namely, high Cu ore, high Co ore, low Co ore, and high Co ore with mica. Effect of FeCl2 concentrations in HCl solutions involving 35.06 g; 70.13 g; and 105.18 g corresponding to 0.25 M; 0.5 M; and 0.75 M respectively, were studied and the reactions mechanism established. It was found that an increase in FeCl2 concentration increases the Co dissolution due to the reduction of Co3+ into Co2+ which is soluble. High Co extractions of 99%, 99%, 99%, and 95% were obtained when mixtures 1 M HCl + 105.18 g FeCl2 were used as lixiviants for high Cu ore, high Co ore, low Co ore, and high cobalt ore with mica, respectively. Copper recoveries of 88%, 77%, 75%, and 86% were obtained for high Cu ore, high Co ore, low Co ore, and high Co ore with mica, respectively. The increase in FeCl2 concentration did not have any important effect on the Cu extraction. Mechanisms of involved reactions were established. The order of cobalt leaching reaction was found to be 2 with respect to cobalt concentration. Optimum leaching conditions were found to be: leaching time: 30 minutes, reagent concentrations: mixture 1 M HCl + 105.18 g FeCl2, S/L ratio = 1:20, stirring speed avoiding the vortex, room temperature, pH values from 2.28 to 0.03, and ORP values from 0.402 to 0.322 V.

Many articles have been written on the effect and potential benefit of cost reduction, downsizing and expense management. Most of these articles have conflicting messages, some even internally within the same article.The objective of this research was to critically evaluate these articles and to see if there was any evidence of the economic effects of cost reduction from the South African experience. The evaluation of the articles was done by a process of deductive reasoning with some help from the principles found within the application of the Theory of Constraints. The research further used a quantitative design to analyse the effect of a cost reduction event on certain ratios and the share price performance relative to an appropriate index over a period of six years after the event.The research has shown that at least some of the academic articles on this subject made different implicit assumptions during the research process. The results from the quantitative research have shown that there were no significant evidence of any effect on the ratios and share price performance from the South African market experience. / Dissertation (MBA)--University of Pretoria, 2013. / Gordon Institute of Business Science (GIBS) / unrestricted

Biomass from forestry and agricultural sources has recently drawn a lot of attention as a new source of feedstock for energy and bio products. Size reduction is an important step in preparation of biomass as a feedstock. Each conversion process needs its own specific size or size distribution of particles. Modeling the size reduction process helps to optimize the design and control of the process while ensuring biomass particle sizes for an efficient biofuel conversion process. The objective of this study was to apply the population balance method for modeling the size reduction process. The model was applied to switchgrass size reduction by a grinder. Two population balance parameters, grinding rate (s⁻¹) and breakage distribution function (dimensionless) were estimated using experimental grinding data. The time dependent balance equations were solved using the Euler technique. The accumulation and depletion of the particles belonging to each size category were simulated as a function of time. The simulation predicted the residence time of particles inside the grinder in a way that the ground particles could meet the size and size distribution specifications for the downstream process. The thesis also describes preliminary steps in size reduction. Ground particles were fractionated based on their size by sieving. Weibull distribution was found to be the best probability density function to fit the data. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Nurses who work with people who use drugs in the Downtown Eastside of Vancouver (DTES), British Columbia are on the forefront in advancing a harm reduction framework in very controversial, cutting-edge practice environments. The purpose of this study was to explore how these nurses, using the framework of harm reduction, make sense of their nursing practice. It is hoped that the results of this study may advance adopting a harm reduction framework in nursing practice, education and policy development and serve as the foundation for further nursing research. This study utilized a qualitative interpretive descriptive methodology to gather data from eight nurses who work with people who use drugs in harm reduction practice environments. The nurses were divided into two focus groups and data was collected through a semi-structured focus group interview. Following initial data analysis, each focus group was reconvened and a second semi-structured group interview was held to clarify and to further discuss the emerging themes. The data analysis proceeded simultaneously with the interviews utilizing a process of constant comparative analysis. I completed the thematic analysis as I moved between the transcripts and identified commonalties and variations within the emerging themes. Ultimately, I described one overarching theme, which encapsulated the range of experiences described by the nurses. The theme that I identified was: meeting people where they are at. The importance to the nurses of both the therapeutic nurse-client relationship and a commitment to praxis were apparent. In conclusion, the value the nurses placed on "meeting people where they are at" was integral in gaining an understanding of how they make sense of their nursing work. / Applied Science, Faculty of / Nursing, School of / Graduate

Despite thirty published evaluation reports citing the effectiveness of Vancouver’s safe injection site (Small 2008), the Canadian federal government refuses to endorse safe injection sites as a health service option available to injection drug users (IDUs). Insite’ s evaluation results are undergoing debate, because two communicative spheres of knowledge, each with a unique authoritative language, are conflicting as each is attempting to gain moral authority over the right to recontextualize drug users. Drawing on a literature review of two harm reduction programs in Vancouver, Insite and Sheway, and expert interviews with evaluators, I show that what constitutes “evidence” is in fact subjective, determined by spheres of communicability that are built upon social, professional and political contexts. To confront the problematic nature of this issue, I suggest that evaluators and overseers need to treat program evaluation as a process of negotiation, best approached in a fluid manner. By obscuring multiple user experiences in the evaluation of harm reduction programs, evaluators and overseers risk imposing their communicative ideologies on what it means to be a drug user. / Arts, Faculty of / Anthropology, Department of / Graduate