No description available.

No description available.

No description available.

Alkaline pressure oxidation, particularly in the presence of trona as additive, can be used to oxidize high carbonate refractory gold ores as it prevents the formation of CO2 in the autoclave. However, the presence of silica in the ore can lead to the encapsulation of pyrite due to the formation of a passive layer. This phenomenon occurs due to the high solubility of silica in alkaline solutions and its subsequent re-precipitation on the reacting pyrite surface. The present study investigated the chemical composition and thickness of the passive layer on a rotating pyrite surface in an aqueous slurry containing silica sand, sodium carbonate and calcium carbonate at 230°C and under 7 bar of oxygen overpressure. Results obtained from XPS and SEM show that a concentration of 2.5 g/L sodium carbonate gave the maximum thickness of passivation on pyrite and that the passive layer consisted primarily of silicates and aluminosilicates.

No description available.

Heme is essential for numerous enzymes involved in the regulation of vascular tone; it is an integral component of nitric oxide synthase and soluble guanylyl cyclase, and is the substrate for heme oxygenase, enzymes critical for vasodilation. Inhibition of heme synthesis is anticipated to result in a deficiency in these hemoproteins, causing disturbances in the tissue’s ability to regulate vascular tone. Hypertension is frequently associated with the morbidity of both porphyria and lead poisoning, two conditions wherein heme biosynthesis is disrupted. The hypothesis tested was, that extended pharmacological inhibition of heme synthesis disrupts normal vascular control and induces hypertension. Rats were treated with SA, a heme synthesis inhibitor, for two weeks; this depleted heme stores of the liver, kidney, spleen and vasculature by up to 62.2%. A significant decrease in hematocrit, hemoglobin, urine nitrate levels, NOS activity and sGC activity were also produced, indicating compromised hemoprotein synthesis and function. Ex vivo studies of blood vessels revealed blunted sensitivity to nitric oxide donors. Lastly, SA treatment produced a significant increase in left ventricular mass, which is indicative of altered cardiac output and blood pressure elevation. Next, telemetry devices were used to determine in vivo blood pressure and salt-sensitivity of blood pressure of rats treated with SA for 33 days. Hemodynamic changes were minimal, yet there was a mild decrease in pressure over two weeks of SA treatment alone. The change from low to high salt diet in SA rats showed no difference compared to control rats. A small increase was observed in 3 mg/kg L-NAME plus high salt compared to high salt alone, while there was no change at this dose in control animals. Heme tissue and blood content was depleted by up to 47%, but was less than two-week experiments. An increase in kidney medulla NOS activity by 19% was observed in vitro compared to controls. Initial two-week experiments were consistent with the hypothesis above, as heme depletion impaired in vivo activity of NOS and sGC and altered vasodilator function. Nevertheless, in vivo results did not support the hypothesis as hypertension and salt-sensitivity of blood pressure were not observed. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2008-06-19 12:32:08.686

No description available.

No description available.

No description available.

<p>A favourable school atmosphere, in which adolescents behave positively, is one of the greatest concerns for teachers, administrators and parents. Although there are several different pressures leading to adolescent misbehaviour at school, the most contributing factors are peer pressure and the socio-economic status of the school. As adolescents enter the school, the peer group then functions as an important socializing agent for them. As peers socialize within their different school environments, individuals are forced to conform to the practices and opinions of the group. Usually this conformity is unconstructive and clashes with the parents&rsquo / and teachers&rsquo / expectations. The aim of this study was to examine the influence of peer pressure on adolescent misbehaviour in advantaged and disadvantaged&nbsp / schools. A quantitative methodological approach was used to conduct the study. The study was conducted with adolescents aged from&nbsp / 13 to 17 years in both advantaged and disadvantaged secondary (high) schools in Windhoek, Namibia. A sample of 300 participants was randomly stratified across the schools. The Exposure to Peer Pressure Control Scale (Allen &amp / Yen, 2002) and Child Behaviour Checklist&nbsp / questionnaires (Achenbach &amp / Edelbrock, 1987) were used to collect the data. Ethical considerations were carefully considered before and during the research procedure of data collection. The reliability of the instruments was checked by means of a pilot study. The data was analysed by means of the Statistical Package for Social Sciences (SPSS) version 18 to reveal descriptive and inferential statistics. Results showed a significant positive relationship between peer pressure and adolescent misbehaviour in schools. In addition, misbehaviour was also positively predicted in both advantaged and disadvantaged schools, with disadvantaged schools being significantly more influential. When comparing peer pressure and adolescent misbehaviours in both advantaged and disadvantaged schools, adolescents in&nbsp / is advantaged schools engaged significantly more in misbehaviour activities and also responded positively more to peer pressure than their counterparts in advantaged schools. Implications for further research were suggested.</p>