A neutron activation analysis procedure for the simultaneous determination of Au, Pd and Ir, and separate determination of Os is described and applied to the determination of these metals in the Mount Albert ultramafic pluton, Quebec. The Mount Albert is an alpine-type ultramafic body whose petrography, geology and geochemistry has been discussed in some detail by MacGregor (1962, 1964). It consists mainly of serpentinized dunite and peridotite. However, it is distinguished by the presence of an eastern lobe which is essentially unserpentinized. In addition to ferromagnesians, two varieties of spinel including disseminated accessory chrome spinel and massive, discordant chromite veins or schlieren are important mineralogical constituents. Twenty samples were analyzed including 5 fresh dunites and peridotites, 8 serpentinized equivalents, 4 disseminated chrome spinels, 1 clinopyroxenite, and 2 massive chromite. The concentrations (in p. p. b.) of average fresh ultramafics and their serpentinized equivalents are:-------------------------------------- ---------------------Pd----Os----Ir----Au------------------------------------------- Fresh rocks------------7.7----7.2--2.5--0.99------------------------------------------- Serpentinized rocks---10----6.6--2.2---2.4-------------------------------------------- The piuton was intruded as a nearly solid mass of olivine and some orthopyroxene with about 15 weight per cent melt. A small concentration of the precious metals, a factor of 2 to 3, in the melt relative to crystalline phases appears to have occurred. The disseminated chrome spinel and massive chromite appear to concentrate the precious metals. In particular, Os and Ir content of the massive chromite is approximately 10 times that of fresh or serpentinized whole rocks. There is little change in average precious metal content with serpentinization. Pd shows a slight increase, and Ir and Os slight decreases in concentration with degree of serpentinization. Only Au appears significant to be enriched in serpentinized rocks where a twofold increase occurs. The variation in precious metal content of all four metals increase when the rocks are serpentinized: When normalized to chondrite meteorites, the precious metal data give fractionation trends similar to that of average chondrite. These trends are compatible with a model in which alpine ultramafics are regarded as residua from the partial melting of parental material of approximately chondritic composition. / Thesis / Master of Science (MSc)

No description available.

L’hydrosilylation d’alcènes est une réaction clé pour la synthèse d’huiles silicones fonctionnelles et d’élastomères silicones nécessite un catalyseur. Industriellement, le platine est utilisé or le coût important de ce métal motive la recherche de catalyseurs alternatifs plus compétitifs, notamment à base de métaux non précieux. Les travaux ont débuté sur des systèmes développés précédemment au laboratoire à base de cobalt et de nickel à haut degré d’oxydation et de ligands dicétones. Les cinétiques de réticulation ont été également suivies aussi bien par des mesures qualitatives d’arrêt d’agitation que par des mesures de rhéologie ou de chaleur de réaction par DSC. Ces catalyseurs sont actifs et robustes pour la réticulation. A la suite, des catalyseurs à base de cobalt portant en particulier des ligands amidures ont été étudiés. Associés à un ligand bidentate (P,N), les systèmes catalytiques sont compétitifs au platine de Karstedt pour l’hydrosilylation sélective d’alcènes. Ces catalyseurs réalisent également la réticulation d’huiles silicones à relativement basse température (20 min à 90°C). Un homologue au fer s’est également montré actif pour la réticulation d’huiles silicones démontrant la faisabilité d’une voie catalytique d’hydrosilylation à partir de complexes de fer non toxiques et robustes / Alkene hydrosilylation is a major tool for the synthesis of functionalized silicone oils and silicone elastomers and is catalyzed by transition metal complexes. Industrially, Platinum complexes are used. However, high and volatile cost and rarity of precious metals lead to the development of competitive alternative systems, especially catalysts based on non-precious transition metals. First, Nickel and Cobalt high-oxidation-state complexes bearing diketone ligands were studied. Those systems had been previously developed in the laboratory and the study has been completed. Crosslinking kinetics were followed by qualitative measures of “stop-stirring” time and by rheology and thermal analysis (DSC). Those catalysts are active over oxygen and stable for silicone-oil crosslinking. Then, Cobalt Catalysts bearing amido-based ligands were studied. When associated with a ligand (phosphino pyridine P,N), those systems are competitive with the Karstedt catalyst (Pt) for selective alkene hydrosilylation. They also allow for silicone-oil crosslinking at relatively low temperature (20 min at 90 °C). Finally, a homologous complex based on Iron was synthesized and showed activity for silicones’ crosslinking evidencing the feasibility of a catalytic hydrosilylation pathway from non-toxic and robust iron complexes.

Thesis (M. Soc. Sc.)--University of Hong Kong, 1984.

Thesis (M.Soc.Sc.)--University of Hong Kong, 1984. / Also available in print.

Submitted by Olivier Boileau (olivier.boileau@hotmail.fr) on 2016-02-18T13:44:30Z No. of bitstreams: 1 Final-Report-FGV-by-Olivier-Boileau.pdf: 1435700 bytes, checksum: 5726e91bb0509cf4b3f5afd9acd70f3b (MD5) / Approved for entry into archive by Ana Luiza Holme (ana.holme@fgv.br) on 2016-02-18T13:45:44Z (GMT) No. of bitstreams: 1 Final-Report-FGV-by-Olivier-Boileau.pdf: 1435700 bytes, checksum: 5726e91bb0509cf4b3f5afd9acd70f3b (MD5) / Made available in DSpace on 2016-02-18T13:53:32Z (GMT). No. of bitstreams: 1 Final-Report-FGV-by-Olivier-Boileau.pdf: 1435700 bytes, checksum: 5726e91bb0509cf4b3f5afd9acd70f3b (MD5) Previous issue date: 2016-02-19 / Using regression and correlation approaches covering the last twenty years of daily data for seven countries, this thesis investigates safe haven and hedge abilities of precious metals against international equities over a given state of the economy. Furthermore, this thesis examines different portfolios performance in-samples and out-of-samples with the aim to observe whether investing in precious metals can help to mitigate investor risk management. The key results are: (i) Gold is the finest precious metal for international hedging against equities (ii) Gold provides valuable portfolio risk management benefits (iii) 60/40 portfolios allocated with gold proffer good investor outcomes. / Recorrendo a duas abordagens diferentes, regressão e correlação, e cobrindo os últimos vinte anos de dados diários para sete países, esta tese investiga as propriedades "safe haven" e "hedge" dos metais preciosos, em comparação com acções internacionais para um dado estado da economia. Adicionalmente, esta tese avalia o desempenho de diferentes portfolios, dentro e fora da amostra, com o objectivo de verificar se o investimento em metais preciosos poderá ajudar a atenuar a gestao do risco por parte do investidor. Os principais resultados são os que se seguem: (i) O ouro é o melhor metal precioso para um "hedging" internacional em oposição às acções (ii) O ouro permite obter valiosos benefícios de gestão de risco do portfolio (iii) 60/40 dos portofios atribuidos com ouro permitem ao investidor obter bons resultados.

Traditional Asian theatre genres have fascinated western audiences since the end of the 19th century. In my thesis, I focused on the means by which Jiří Frejka, a leading representative of Czech avant- garde theatre, dealt with that trend. Through Japanese, Chinese and Indian texts, he verifies new possibilities of all elements of theatre production - the stage, music and, primarily, the actor and his voice and movement. Thanks to prompt books, photographs, reviews and other materials from Frejka's estate stored in the National Museum, the archive of the National Theatre and the Moravian Museum in Brno, I assess these individual elements of theatre production in connection with traditional Asian genres and I seek mutual parallels, sources of inspiration and, primarily, the manner in which Frejka adapted them to his own directorial work. The objective of this work is to confirm the previous thesis that, in the case of Jiří Frejka, deeper study of the topic led to a fundamental shift in the manner of bringing these "foreign" sources of inspiration into the Czech environment, which moved away from a merely decorative function toward an internally linked and well-founded method. Key words Czech theatre avant-garde, Asagao, Modern Studio, Lady Precious Stream, Shakuntala, The Post Office

Previous mineralogical investigations (QemSCAN) performed on all effluent flotation streams of Mimosa mine (Zimbabwe) indicated the presence of appreciable amounts of platinum group minerals (PGMs), which are not recovered. Most, generally in excess of 70%, of the liberated PGMs in these streams belonged to the Pt-Pd-Bi-Te class in all the samples investigated. In the first part of this work, electrochemical investigations, electrochemically-controlled contact angle measurements and Raman spectroscopy have been employed to investigate the interaction of ethyl xanthate with Pd-Bi-Te and PtAs2. Impedance measurements showed lower capacitance values in solutions containing KEX indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction, hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. The result of this investigation has shown dixanthogen to be present on both the minerals (PtAs2 and Pd-Bi-Te) when the surfaces are anodically polarized. Chemisorbed xanthate could be identified within 120 seconds yielding a hydrophobic surface as indicated by electrochemically-controlled contact angle measurements. Maximum contact angles of 63o were measured in the case Pd-Bi-Te. As a result the mineral surface is expected to be hydrophobic and a lack of collector interaction with the mineral is not the reason for low PGM recoveries experienced. Secondly, the flotation recovery of synthetically prepared Pd-Bi-Te was compared with that of chalcopyrite (a typical fast-floating mineral) and pyrrhotite (a typical slow-floating mineral), with microflotation tests. These indicated Pd-Bi-Te to be a fast-floater with flotation rates exceeding that of chalcopyrite. Predicted flotation rate constants (from the Ralston model) were significantly lower for small particles (with diameters similar to those lost to the effluent streams) compared with those of particle with intermediate sizes. This supports the suggestion that losses to effluent streams are caused by particle size effects. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

No description available.

Gemlike objects are a nearly ubiquitous phenomenon in the medium of glass, although culturally specific studies remain scarce. This dissertation considers the production of such works in the early medieval period, primarily in association with Abbasid rule. The first half attends to several accessory issues, including glass-related terminology, glass-coloring treatises, the lives of glassworkers, gemstone connoisseurship, and the legal status of such products. These demonstrate a range of coexisting attitudes, including the desirability of such works for their own sake rather than as surreptitious substitutes for “true” gemstones. The second half focuses on an exemplary object, an opaque turquoise glass bowl from the Treasury of San Marco in Venice, which I propose was produced in Baghdad for the caliph al-Mutawakkil just after the year 850. I then consider this work’s changing reception from late medieval Venice to modern scholarship, including ways in which “correct” interpretations of its material and/or origin have been repeatedly supplanted by false leads. The fundamental argument is that gemlike vessels like the San Marco turquoise were not deceptive stand-ins but rather intended to exercise complex discursive practices, both political and connoisseurial in nature, a function that ultimately remains in effect today.