Há uma grande quantidade de ligas odontológicas no mercado e é difícil para os dentistas escolher qual utilizar. Além disso, não há pesquisas que tenham investigado a influência dos métodos de fundição e da variação de temperatura na biocompatibilidade destes materiais. Então, o objetivo deste estudo foi comparar a biocompatibilidade das ligas odontológicas de metais básicas e do titânio e avaliar se o método de fundição e a mudança de temperatura influenciavam esta biocompatibilidade. A biocompatibilidade e a influência dos métodos de fundição foram avaliadas através de testes de contato direto e a influência da temperatura por testes em extratos. Para os testes de contato direto, discos de Ni-Cr, Ni-Cr-Be, Co-Cr-Mo, Co-Cr-Mo-W e Ni-Cr-Ti foram fundidos por dois métodos: plasma, sob atmosfera de argônio com injeção da liga no molde por vácuo-pressão; e chama de gás oxigênio, com injeção da liga no molde por centrifugação. Ti-6Al-4V e Ti cp foram fundidos por plasma. Os discos foram polidos, limpados e autoclavados. Células SCC9 foram cultivadas em meio de cultura D-MEM/HF12 suplementado sobre os discos; poços sem discos foram usados como controle negativo e fenol como controle positivo. Após período de 48 horas e 18 dias, o número de células e a viabilidade celular foram avaliados. Nos testes em extratos, discos limpos e autoclavados de Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V e Ti cp fundidos por plasma foram imersos em saliva artificial previamente filtrada para obtenção dos extratos e divididos em dois grupos: um foi submetido a 1700 ciclos térmicos, durante um período de 24 dias; e o outro foi mantido em 37°C durante o mesmo período. Depois deste período, os discos foram separados da saliva. Células foram cultivadas em placas de 24 poços até atingirem subconfluência. Então a saliva foi colocada na cultura de células durante 6 horas, e após este período, o número de células e a viabilidade celular foram avaliados. Os resultados foram submetidos a teste estatístico apropriado. Os resultados dos testes de contato direto mostraram que Ti cp e Ti-6Al-4V foram os mais biocompatíveis, seguidos pela liga de Ni-Cr, que teve bons resultados em ambos os métodos de fundição. Os piores resultados para os materiais fundidos por chama de gás oxigênio foram da liga à base de Ni-Cr-Be. Não houve diferenças significativas entre os métodos de fundição. Na avaliação dos testes em extratos, os ciclos térmicos foram significativos somente para a liga Ni-Cr-Ti. Não houve diferenças significativas entre os extratos submetidos aos ciclos térmicos, mas entre os extratos mantidos em 37°C, a liga à base de Ni-Cr e o Ti cp mostraram os piores resultados. Os resultados sugerem que Ti cp e Ti-6Al-4V foram biocompatíveis e Ni-Cr-Be foi citotóxica. O método de fundição não foi significante para a biocompatibilidade e a variação de temperatura é significativa para a liga à base de Ni-Cr-Ti. / There is a large number of dental alloys in the market and it is difficult for the dentists to choose which to use. Besides, there are not researches that has investigated the influence of casting methods and the variation of temperature in the biocompatibility of these materials. Then, the aim of this study was to compare the biocompatibility of base-metal alloys and titanium and to evaluate if the casting method and change of temperature influenced this biocompatibility. The biocompatibility and the influence of casting methods were analyzed by direct contact and the influence of temperature by tests on extracts. For direct contact tests, disks of Ni-Cr, Ni-Cr-Be, Co-Cr-Mo, Co-Cr-Mo-W, Ni-Cr-Ti were casted by two methods: plasma, under argon atmosphere, injected by vacuum-pressure; and oxygen gas flame, injected by centrifugation. Ti-6Al-4V and CP Ti were casted by plasma. After casting, the disks were polished, cleaned and autoclaved. SCC9 cells were cultured in culture media D-MEM/HF12 supplemented, on the disks; empty wells were used as a negative control and phenol as a positive control. After a period of 48 hours and 18 days, the number of cell and its viability were evaluated. In the tests on extracts, clean and autoclaved disks of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V alloys and CP Ti casted by plasma were immersed in filtered artificial saliva for extraction and divided in two groups: one was subjected to 1700 thermal cycles, during a period of 24 days; and the other was maintained in 37° C during the same period. After this period, the disks were separated from saliva. Cells were cultured until the subconfluence. Then the saliva was put in the cell culture for 6 hours, and after this period, the number of cell and cell viability was evaluated. The results were submitted to the apropriate statistical analysis tests. The results of the direct contact tests showed that CP Ti and Ti-6Al-4V were the most biocompatible, followed by Ni-Cr alloy, which had good results in both casting methods. The worst results for oxygen gas flame were of Ni-Cr-Be. There was no significant differences between casting methods. In the evaluation of tests on the extracts, the thermal cycles were significant only for Ni-Cr-Ti alloy. There were no significant differences among the extracts subjected to thermal cycles, but in the extracts maintained in 37°C, the Ni-Cr and CP Ti showed the worst results The results suggest that the CP Ti and Ti-6Al-4V were biocompatible and the Ni-Cr-Be was cytotoxic. The casting method was not significant for biocompatibility and the variation of temperature was significant for Ni-Cr-Ti alloy.

The objectives of this research are to accomplish Multilayer Ceramic Capacitors, MLCCs used Temperature compensated type Ceramic powder and different design and size to confer its characteristic. The first to speak about Taiwan capacitors property development to point Multilayer Ceramic Capacitors from 1960 to recently.The manufacture procedure from Normal Metal Electronic procedure change to Base Metal Electronic procedure. The second to quote the relation document to explain Temperature compensated type Multilayer Ceramic Capacitors characteristics and main electric characteristics and the related factors such as Frequency, Test Signal Level, DC Bias, Temperature, Time, Insulation resistance and Break down voltage. The last from sample manufacture flow and structure analysis to electric characteristic measure analysis and result to discuss opposite factor characteristics. To bring up develop direction and reference material.

Há uma grande quantidade de ligas odontológicas no mercado e é difícil para os dentistas escolher qual utilizar. Além disso, não há pesquisas que tenham investigado a influência dos métodos de fundição e da variação de temperatura na biocompatibilidade destes materiais. Então, o objetivo deste estudo foi comparar a biocompatibilidade das ligas odontológicas de metais básicas e do titânio e avaliar se o método de fundição e a mudança de temperatura influenciavam esta biocompatibilidade. A biocompatibilidade e a influência dos métodos de fundição foram avaliadas através de testes de contato direto e a influência da temperatura por testes em extratos. Para os testes de contato direto, discos de Ni-Cr, Ni-Cr-Be, Co-Cr-Mo, Co-Cr-Mo-W e Ni-Cr-Ti foram fundidos por dois métodos: plasma, sob atmosfera de argônio com injeção da liga no molde por vácuo-pressão; e chama de gás oxigênio, com injeção da liga no molde por centrifugação. Ti-6Al-4V e Ti cp foram fundidos por plasma. Os discos foram polidos, limpados e autoclavados. Células SCC9 foram cultivadas em meio de cultura D-MEM/HF12 suplementado sobre os discos; poços sem discos foram usados como controle negativo e fenol como controle positivo. Após período de 48 horas e 18 dias, o número de células e a viabilidade celular foram avaliados. Nos testes em extratos, discos limpos e autoclavados de Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V e Ti cp fundidos por plasma foram imersos em saliva artificial previamente filtrada para obtenção dos extratos e divididos em dois grupos: um foi submetido a 1700 ciclos térmicos, durante um período de 24 dias; e o outro foi mantido em 37°C durante o mesmo período. Depois deste período, os discos foram separados da saliva. Células foram cultivadas em placas de 24 poços até atingirem subconfluência. Então a saliva foi colocada na cultura de células durante 6 horas, e após este período, o número de células e a viabilidade celular foram avaliados. Os resultados foram submetidos a teste estatístico apropriado. Os resultados dos testes de contato direto mostraram que Ti cp e Ti-6Al-4V foram os mais biocompatíveis, seguidos pela liga de Ni-Cr, que teve bons resultados em ambos os métodos de fundição. Os piores resultados para os materiais fundidos por chama de gás oxigênio foram da liga à base de Ni-Cr-Be. Não houve diferenças significativas entre os métodos de fundição. Na avaliação dos testes em extratos, os ciclos térmicos foram significativos somente para a liga Ni-Cr-Ti. Não houve diferenças significativas entre os extratos submetidos aos ciclos térmicos, mas entre os extratos mantidos em 37°C, a liga à base de Ni-Cr e o Ti cp mostraram os piores resultados. Os resultados sugerem que Ti cp e Ti-6Al-4V foram biocompatíveis e Ni-Cr-Be foi citotóxica. O método de fundição não foi significante para a biocompatibilidade e a variação de temperatura é significativa para a liga à base de Ni-Cr-Ti. / There is a large number of dental alloys in the market and it is difficult for the dentists to choose which to use. Besides, there are not researches that has investigated the influence of casting methods and the variation of temperature in the biocompatibility of these materials. Then, the aim of this study was to compare the biocompatibility of base-metal alloys and titanium and to evaluate if the casting method and change of temperature influenced this biocompatibility. The biocompatibility and the influence of casting methods were analyzed by direct contact and the influence of temperature by tests on extracts. For direct contact tests, disks of Ni-Cr, Ni-Cr-Be, Co-Cr-Mo, Co-Cr-Mo-W, Ni-Cr-Ti were casted by two methods: plasma, under argon atmosphere, injected by vacuum-pressure; and oxygen gas flame, injected by centrifugation. Ti-6Al-4V and CP Ti were casted by plasma. After casting, the disks were polished, cleaned and autoclaved. SCC9 cells were cultured in culture media D-MEM/HF12 supplemented, on the disks; empty wells were used as a negative control and phenol as a positive control. After a period of 48 hours and 18 days, the number of cell and its viability were evaluated. In the tests on extracts, clean and autoclaved disks of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V alloys and CP Ti casted by plasma were immersed in filtered artificial saliva for extraction and divided in two groups: one was subjected to 1700 thermal cycles, during a period of 24 days; and the other was maintained in 37° C during the same period. After this period, the disks were separated from saliva. Cells were cultured until the subconfluence. Then the saliva was put in the cell culture for 6 hours, and after this period, the number of cell and cell viability was evaluated. The results were submitted to the apropriate statistical analysis tests. The results of the direct contact tests showed that CP Ti and Ti-6Al-4V were the most biocompatible, followed by Ni-Cr alloy, which had good results in both casting methods. The worst results for oxygen gas flame were of Ni-Cr-Be. There was no significant differences between casting methods. In the evaluation of tests on the extracts, the thermal cycles were significant only for Ni-Cr-Ti alloy. There were no significant differences among the extracts subjected to thermal cycles, but in the extracts maintained in 37°C, the Ni-Cr and CP Ti showed the worst results The results suggest that the CP Ti and Ti-6Al-4V were biocompatible and the Ni-Cr-Be was cytotoxic. The casting method was not significant for biocompatibility and the variation of temperature was significant for Ni-Cr-Ti alloy.

Hydrothermal fluid circulation is an important process in the formation and evolution of ocean crust. A tectonic window located at Pit Deep (NE corner Easter Microplate) provides an ideal location to examine a 3-dimensional view of ocean crust formed at the fast-spreading East Pacific Rise. This study focuses on the base metal (Cu, Ni, Mn, Co, Zn, and Pb) content of the bulk rock and mineral components in the sheeted dike complex. There is no observable trend of metal mobility with depth, geographic location, or dominant alteration phase. Secondary mineral analyses (using LA-ICP-MS) show that metals are redistributed throughout the sheeted dikes, entering into secondary sulphides, chlorite, and amphibole. Temperature and mineral stability is a primary control of metal mobility in these rocks. Due to highly variable metal concentrations and observed temperatures of alterations, the hydrothermal cell is suggested to be a continuously evolving system, and can cause the large variability observed in the metal distribution in the sheeted dikes. / Graduate / 0996 / 0411 / 0372

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Sulphuric acid/oxygen pressure leaching is typically employed on Base Metal Refineries (BMRs) to selectively dissolve base metals from platinum group metal (PGM) bearing nickelcopper matte. Optimal operation of this processing step requires an understanding of the system chemistry and the effects of process variables on base metal and PGM leaching behaviour. This project aimed to aid in the development of an improved understanding of the high pressure leaching system. The effects of temperature, pressure, acid concentration, and solid to liquid ratio on the leaching behaviour were determined experimentally using a two litre autoclave. For conditions comparable to that typically used at the Western Platinum Ltd. BMR, changes in the acid concentration had the largest effect on the copper leaching behaviour. Increasing the initial acid concentration from 140 g H2SO4/ℓ to 165 g H2SO4/ℓ resulted in the copper dissolution decreasing from 88.7% to 75.3% on average for the experiments performed at different temperatures (116°C, 130°C) and pressures (7 bar, 9 bar), and with different solids contents (80 g/ℓ, 130 g/ℓ). In the case of the other precious metals (OPMs), temperature was determined to be the process variable with the largest effect on the leaching kinetics. The average percentage rhodium dissolution achieved after seven hours of leaching at different conditions (pressure, acid concentration, and solids content were varied) increased from 58.3% at 116°C to 83.6% at 130°C. Similar effects were observed for ruthenium (96.2% dissolution at 130°C; 79.4% dissolution at 116°C) and iridium (81.8% dissolution at 130°C; 46.9% dissolution at 116°C). The rate of copper leaching was found to be limited by the rate of oxygen transfer from the gaseous phase to the liquid phase, while the remainder of the reactions were chemical reaction limited. The extent of OPM leaching was found to be dependent on the rate and extent of copper leaching. A set of 21 chemical reactions was proposed to describe the leaching behaviour, and the shape factors and reaction rate constants were determined by the method of least squares to minimise the error between the predicted concentrations and the experimental data. Apart from direct base metal leaching reactions, six cationic exchange reactions contribute to the leaching of copper sulphides and nickel sulphides by precipitation of OPM oxides. Three leaching reactions for each of the OPMs (one for sulphide phases, one for metallic phases, and one for oxide phases) resulted in satisfactory modelling of the system behaviour. Activation energies of -26.2 kJ/mol and -5.9 kJ/mol were calculated for the digenite acid leaching reaction and the covellite direct oxidation reaction, respectively, which confirmed that the rates of these reactions were mass transfer limited. The activation energies for the remainder of the base metal leaching reactions exceeded 30 kJ/mol. The activation energies of the reactions accounting for rhodium sulphide leaching, rhodium leaching, and rhodium oxide leaching, were calculated to be 64.2 kJ/mol, 138.5 kJ/mol, and 116.2 kJ/mol, respectively. Similar activation energies were calculated for the respective Ru and Ir leaching reactions. The rate of OPM sulphide leaching was typically an order of magnitude and three orders of magnitude larger than the rate of OPM leaching reactions and OPM oxide leaching reactions, respectively. The autoclave at the Western Platinum Ltd. BMR was modelled assuming a monosized distribution of the feed and approximating the autoclave as four ideal continuously stirred tank reactors. The steady state solution employed the sequential modular approach in MATLAB, while the dynamic simulation involved solving a set of 217 differential equations derived from mass and energy balances simultaneously in MATLAB. The model was used successfully to evaluate the effects that changes in the leaching temperature, leaching pressure, acid feed rate, and solids feed rate have on the extent of base metal and OPM leaching in the autoclave. The optimum operating conditions depend on the flow rates and compositions of the feed streams. A feed stream containing 10.3 wt% solids (825 kg solids/h) and an acid addition rate of 28.6 kg/h were considered as typical operating conditions for model-based analysis. More than 95% copper dissolution and no OPM dissolution were predicted when performing the pressure leaching at a pressure of 8 bar and a temperature of approximately 123°C. Decreasing the pressure resulted in lower copper dissolution when OPM leaching started to occur. Increasing the temperature resulted in reduced copper leaching, while decreasing the temperature resulted in a longer OPM leaching period and hence higher OPM dissolution. Model-based analysis furthermore showed that the relative amounts and relative leaching rates of digenite and covellite significantly influence the percentage copper dissolution achieved when noticeable OPM leaching start to occur. / AFRIKAANSE OPSOMMING: Swawelsuur/suurstof hoë druk loging word tipies op Basis Metaal Raffinaderye (BMRe) gebruik om basis metale selektief op te los vanuit platinum groep metaal (PGM) bevattende nikkel-koper mat. Optimale bedryf van hierdie prosesstap vereis ʼn begrip van die sisteem se chemie en die effekte wat proses veranderlikes op die logingsgedrag van basis metale en PGMe het. Hierdie projek het ten doel gehad om ʼn beter begrip van die hoë druk loging sisteem te ontwikkel. Die effekte van temperatuur, druk, suur konsentrasie, en vastestof tot vloeistof verhouding op die logingsgedrag is eksperimenteel met behulp van ʼn twee liter outoklaaf bepaal. Vir toestande vergelykbaar met dié wat tipies by die Western Platinum Bpk. BMR gebruik word, het veranderinge in die suurkonsentrasie die grootste effek op die logingsgedrag van koper gehad. Verhoging van die aanvanklike suurkonsentrasie van 140 g H2SO4/ℓ na 165 g H2SO4/ℓ het tot gevolg gehad dat die gemiddelde koper oplossing afgeneem het van 88.7% na 75.3% vir die eksperimente wat by verskillende temperature (116°C, 130°C) en drukke (7 bar, 9 bar), en met verskillende vastestof inhoud (80 g/ℓ, 130 g/ℓ), uitgevoer is. In die geval van die ander edelmetale (AEM) is bevind dat die temperatuur die prosesveranderlike met die grootste effek op die logingskinetika is. Die gemiddelde persentasie rodium oplossing wat na sewe ure se loging by verskillende toestande (druk, suurkonsentrasie, en vastestof inhoud is varieer) behaal is, het toegeneem van 58.3% by 116°C na 83.6% by 130°C. Soortgelyke effekte is waargeneem vir rutenium (96.2% oplossing by 130°C; 79.4% oplossing by 116°C) en iridium (81.8% oplossing by 130°C; 46.9% oplossing by 116°C). Dit is bevind dat die tempo van koper loging beperk is deur die tempo van suurstof oordrag vanaf die gas na die vloeistoffase, terwyl chemiese reaksies beperkend was vir die res van die reaksies. Die mate van AEM loging was afhanklik van die tempo en mate van koper loging. ʼn Stel van 21 reaksies is voorgestel om die logingsgedrag te beskryf, en die vorm faktore en reaksie tempo konstantes is bepaal deur middel van die metode van kleinste kwadrate om die fout tussen die voorspelde konsentrasies en die eksperimentele data te minimeer. Afgesien van die direkte basis metaal logingsreaksies het ses kationiese uitruilingsreaksies bygedra tot die loging van kopersulfiede en nikkelsulfiede deur presipitasie van AEM oksiede. Drie logingsreaksies vir elk van die AEMe (een vir die sulfied fase, een vir die metaal fase, en een vir die oksied fase) het bevredigende modellering van die sisteem se gedrag tot gevolg gehad. Aktiveringsenergieë van -26.2 kJ/mol en -5.9 kJ/mol is bereken vir die Cu1.8S suur logingsreaksie en die CuS direkte oksidasie reaksie, onderskeidelik, wat bevestig het dat die tempo’s van hierdie reaksies deur massa oordrag beperk is. Die aktiveringsenergieë vir die res van die basis metaal logingsreaksies het 30 kJ/mol oorskry. Die aktiveringsenergieë vir die reaksies wat die rodiumsulfied loging, rodium loging, en rodiumoksied loging beskryf is as 64.2 kJ/mol, 138.5 kJ/mol, en 116.2 kJ/mol, onderskeidelik, bereken. Soortgelyke aktiveringsenergieë is bereken vir die onderskeie Ru en Ir logingsreaksies. Die tempo van AEM sulfied loging was tipies ʼn ordegrootte en drie ordegroottes groter as die tempo van AEM logingsreaksie en AEM oksied logingsreaksies, onderskeidelik. Die outoklaaf by die Western Platinum Bpk. BMR is gemodelleer deur ʼn enkelgrootte verspreiding vir die voer te aanvaar en die outoklaaf as vier ideale kontinu geroerde tenk reaktore te benader. Die oplossing vir gestadige toestande het die sekwensiële modulêre benadering toegepas in MATLAB, terwyl die dinamiese simulasie die gelyktydige oplos van 217 differensiale vergelykings, wat vanaf massa- en energiebalanse afgelei is, in MATLAB behels het. Die model is suksesvol gebruik om die effekte wat veranderinge in die logingstemperatuur, logingsdruk, suur voertempo, en vastestof voertempo op die mate van basis metaal en AEM loging in die outoklaaf het, te bepaal. Die optimale bedryfstoestande is afhanklik van die vloeitempo’s en samestellings van die voerstrome. ʼn Voerstroom wat 10.3 massa% vastestof (825 kg vastestof per uur) bevat en ʼn suur voertempo van 28.6 kg/h is as tipiese bedryfstoestande beskou vir model-gebaseerde analises. Meer as 95% koper oplossing sonder enige AEM oplossing is voorspel wanneer die loging by ʼn druk van 8 bar en ʼn temperatuur van ongeveer 123°C uitgevoer word. ʼn Vermindering van die druk het tot gevolg gehad dat laer koper loging behaal is toe AEM loging begin plaasvind het. ʼn Verhoging in die temperatuur het laer koper loging tot gevolg gehad, terwyl laer temperature ʼn langer AEM logingsperiode en gevolglik hoër AEM loging tot gevolg het. Model-gebaseerde analises het verder getoon dat die relatiewe hoeveelhede en relatiewe tempo’s van loging van Cu1.8S en CuS ʼn beduidende invloed het op die persentasie koper wat geloog is wanneer beduidende AEM loging begin plaasvind.

GMAW (Gas Metal Arc Welding) is one of the most important arc welding processes being adopted in modern manufacturing industry due to its advantages in productivity, energy efficiency and automation. By monitoring and improving some of the important properties of GMAW such as production rate, metal transfer and base metal heat input, researchers could bring the process efficiency and stability to a new level. In recent years, some innovative modifications of GMAW such as Twins, Tandem and laser-MIG hybrid welding have been adopted into many industrial applications for better productivity. In this dissertation, a novel GMAW called DB-GMAW (Dual Bypass Gas Metal Arc Welding) using two GTAW torches and one GMAW torch to construct a welding system, is proposed and developed. In DB-GMAW, two GTAW torches perform the bypass system which decouples the total welding current into base metal current and bypass current after the melt down of filler wire. Compared to conventional GMAW, DB-GMAW has many advantages in droplet formation, base metal heat input and penetration achievement due to its unique characteristics in welding arc and current flow. In the first place of the research, experimental system of DB-GMAW is constructed. Then, sufficient experiments under different parameters are performed to provide us a good understanding of the behaviors and characteristics of this novel GMAW process. Observation about metal transfer formation and base metal heat input is studied to verify its theoretical analysis. Full penetration of work piece via DB-GMAW is achieved based on a series of parameter testing experiments. Moreover, image processing techniques are applied to DB-GMAW to monitor the welding process and construct a feedback system for control. Considering the importance of maintaining stable full penetration during many welding applications, a nonlinear model of DB-GMAW full penetration is developed in this dissertation. To do that, we use machine vision techniques to monitor the welding profile of the work piece. A control algorithm based on the nonlinear model using adaptive control technique is also designed. The achievement of this dissertation provides a fundamental knowledge of a novel welding process: DB-GMAW, and a good guidance for further studies about DBGMAW.

Objectives: The objectives of this study were to establish the extent of dermal and respiratory exposure at selected locations at a South African platinum mine. The study included exposure to lead oxide fumes in an assay laboratory, nickel sulfate powder at a nickel sulfate crystallizer circuit and packing site and metallic copper dust whilst executing copper stripping. Methods: In an availability study, the dermal metal exposures were measured before, during and at the end of shifts. Dermal exposure samples were taken with GhostwipesTM from the dominant hand, wrist and forehead. Wipes were analyzed using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Wipe samples were taken from surfaces in the workplace and analyzed according to NIOSH 9102, using ICP-AES. Personal and static inhalable dust samples were taken and the dust samples were analyzed according to NIOSH 7300, using ICP-AES. A validated questionnaire was used to evaluate self reported dermatological complaints of the workers at the fire assay laboratory and base metal recovery plant. Results: 100% of the nickel respiratory exposures and 36.8% of the lead respiratory exposures were above the occupational exposure limits (OEL). Copper respiratory exposure was present but less significant with a geometric mean of 0.071 mg m-3. All of the dermal lead measurements and the majority of the nickel and copper dermal measurements were below the limit of detection. Nickel surface contamination was the most significant and ranged between 8.430 μg cm-2 and 387.488 μg cm-2. Only 30% of the copper surface sample results were below the detection limit with a maximum surface sample of 14.41 μg cm-2. Lead surface contamination was low with 90% of the samples below the limit of detection. All of the workers at the nickel crystallizer circuit and packing site had a Dalgard score above 1.3 and therefore are at a higher risk of developing a skin disease. None of the workers at the copper stripping site had a significant Dalgard score and only one worker at the fire assay laboratory had a score above 1.3 and therefore is at a higher risk of developing a skin disease. Conclusions: Recommendations were made to lower the exposure to inhalable lead and nickel. The low lead dermal measurements may be due to adequate personal protective equipment usage and hygiene practices. Although the ethnicity of the workers may be the reason for the low incidence of dermatological complaints, the Dalgard score indicated that five workers are at risk of developing skin diseases. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011

abstract: The search for highly active, inexpensive, and earth abundant replacements for existing transition metal catalysts is ongoing. Our group has utilized several redox non-innocent ligands that feature flexible arms with donor substituents. These ligands allow for coordinative flexibility about the metal centre, while the redox non-innocent core helps to overcome the one electron chemistry that is prevalent in first row transition metals. This dissertation focuses on the use of Ph2PPrDI, which can adopt a κ4-configuration when bound to a metal. One reaction that is industrially useful is hydrosilylation, which allows for the preparation of silicones that are useful in the lubrication, adhesive, and cosmetics industries. Typically, this reaction relies on highly active, platinum-based catalysts. However, the high cost of this metal has inspired the search for base metal replacements. In Chapter One, an overview of existing alkene and carbonyl hydrosilylation catalysts is presented. Chapter Two focuses on exploring the reactivity of (Ph2PPrDI)Ni towards carbonyl hydrosilylation, as well as the development of the 2nd generation catalysts, (iPr2PPrDI)Ni and (tBu2PPrDI)Ni. Chapter Three presents a new C-O bond hydrosilylation reaction for the formation of silyl esters. It was found the (Ph2PPrDI)Ni is the most active catalyst in the literature for this transformation, with turnover frequencies of up to 900 h-1. Chapter Four explores the activity and selectivity of (Ph2PPrDI)Ni for alkene hydrosilylation, including the first large scope of gem-olefins for a nickel-based catalyst. Chapter Five explores the chemistry of (Ph2PPrDI)CoH, first through electronic structure determinations and crystallography, followed by an investigation of its reactivity towards alkyne hydroboration and nitrile dihydroboration. (Ph2PPrDI)CoH is the first reported cobalt nitrile dihydroboration catalyst. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2018

Objectives: The objectives of this study were to establish the extent of dermal and respiratory exposure at selected locations at a South African platinum mine. The study included exposure to lead oxide fumes in an assay laboratory, nickel sulfate powder at a nickel sulfate crystallizer circuit and packing site and metallic copper dust whilst executing copper stripping. Methods: In an availability study, the dermal metal exposures were measured before, during and at the end of shifts. Dermal exposure samples were taken with GhostwipesTM from the dominant hand, wrist and forehead. Wipes were analyzed using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Wipe samples were taken from surfaces in the workplace and analyzed according to NIOSH 9102, using ICP-AES. Personal and static inhalable dust samples were taken and the dust samples were analyzed according to NIOSH 7300, using ICP-AES. A validated questionnaire was used to evaluate self reported dermatological complaints of the workers at the fire assay laboratory and base metal recovery plant. Results: 100% of the nickel respiratory exposures and 36.8% of the lead respiratory exposures were above the occupational exposure limits (OEL). Copper respiratory exposure was present but less significant with a geometric mean of 0.071 mg m-3. All of the dermal lead measurements and the majority of the nickel and copper dermal measurements were below the limit of detection. Nickel surface contamination was the most significant and ranged between 8.430 μg cm-2 and 387.488 μg cm-2. Only 30% of the copper surface sample results were below the detection limit with a maximum surface sample of 14.41 μg cm-2. Lead surface contamination was low with 90% of the samples below the limit of detection. All of the workers at the nickel crystallizer circuit and packing site had a Dalgard score above 1.3 and therefore are at a higher risk of developing a skin disease. None of the workers at the copper stripping site had a significant Dalgard score and only one worker at the fire assay laboratory had a score above 1.3 and therefore is at a higher risk of developing a skin disease. Conclusions: Recommendations were made to lower the exposure to inhalable lead and nickel. The low lead dermal measurements may be due to adequate personal protective equipment usage and hygiene practices. Although the ethnicity of the workers may be the reason for the low incidence of dermatological complaints, the Dalgard score indicated that five workers are at risk of developing skin diseases. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows: • Irradiated (Unit 4), • irradiated and recovery annealed (Units 2 and 3), and • irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam. Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined: • The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed. • KJc values of the weld metals generally followed the course of the MC though with a large scatter. • There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. • The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front. • The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals. • A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner. • It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal. • The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.