The corrosion susceptibility of selected metallic materials frequently employed in prosthetic dentistry has been examined with electrochemical methods. Results have been compared with data derived from breakthrough potential measurements performed with these materials before. Mostly agreement and/or close correlation were found, discrepancies are discussed and tentatively assigned to the different experimental conditions.

[pt] O Brasil é o segundo maior produtor de lixo eletrônico das Américas, com uma produção que cresce a cada ano e apenas 10 por cento dela sendo tratada de forma apropriada. Adicionalmente, o Brasil não possui tecnologia própria para tratamento de placas de circuito impresso, componente chave presente neste tipo de resíduo. Atualmente, o Brasil não possui uma planta industrial voltada para essa atividade extrativista a partir de resíduos eletrônicos, sendo a maior parte do seu tratamento realizado no exterior. A hipótese de pesquisa deste manuscrito é que as universidades e suas comunidades poderiam desenvolver fontes de matéria-prima para tais processos de extração e, portanto, merecem atenção para a criação de pontos de coleta e parcerias. Nesse contexto, é necessário entender o comportamento dessa comunidade em relação à aquisição, armazenamento e descarte de equipamentos eletrônicos, bem como informações sobre temas relacionados ao gerenciamento e reciclagem de resíduos eletrônicos. Adicionalmente, criou-se uma rota conceitual de tratamento, a partir da integração de tecnologias descritas na literatura. Após a criação do design da rota, foi realizado um balanço de massa e energia, considerando dois casos base de fonte de placas de circuito impresso como matéria prima matéria prima: A) Lixo eletrônico em geral; B) utilizando somente celulares. Para ambos os casos, foi considerado o tratamento de 2 t/h. Determinou-se que o grupo estudado possui mais de 16,96 milhões de telefones celulares em hibernação, além de outros equipamentos, com valor de estoque estimado em 67,45 milhões de dólares para o grupo estudado na região metropolitana do Rio de Janeiro. Se extrapolado para todo o Brasil, pode chegar a 797,50 milhões de dólares para o grupo estudado. uma taxa interna de retorno de 141,6 por cento e 3990,7 por cento para o caso A e B, respectivamente e valor presente líquido de USD 44,834,616 e USD 3,215,300,083 para o caso A e B, respectivamente. Adicionalmente, foi determinado que o caso A possui uma grande sensibilidade a variação da taxa de ocupação. Neste contexto, a presente pesquisa tem o potencial de ajudar na criação da primeira planta industrial brasileira voltada para a reciclagem de placas de circuito impresso, assim como entender quais são as variáveis chaves para o processamento destes componentes. Adicionalmente, o projeto apresenta o investimento necessário para a criação da planta, sendo uma informação crucial para potenciais investidores. / [en] Brazil is the second largest producer of electronic waste in the Americas, with a production that grows each year and only 10 percent of it is properly treated. Additionally, Brazil does not have its own technology for treating printed circuit boards, a key component present in this type of waste. Currently, Brazil does not have an industrial plant dedicated to this extractive activity from electronic waste, with most of its treatment carried out abroad. The research hypothesis of this manuscript is that universities and their communities could develop raw material sources for such extraction processes and, therefore, deserve attention for the creation of collection points and partnerships. In this context, it is necessary to understand the behavior of this community in relation to the acquisition, storage and disposal of electronic equipment, as well as information on issues related to the management and recycling of electronic waste. Additionally, a conceptual treatment route was created based on the integration of technologies described in the literature. After creating the route design, a mass and energy balance was carried out, considering two base cases of printed circuit boards as raw material: A) Electronic waste in general; B) using cell phones only. For both cases, the treatment of 2 t/h was considered. It was determined that the studied group has more than 16.96 million cell phones in hibernation, in addition to other equipment, with an estimated inventory value of 67.45 million dollars for the studied group in the metropolitan region of Rio de Janeiro. If extrapolated to all of Brazil, it could reach 797.50 million dollars for the studied group. an internal rate of return of 141.6 percent and 3990.7 percent for case A and B, respectively, and net present value of USD 44,834,616 and USD 3,215,300,083 for case A and B, respectively. Additionally, it was determined that case A is highly sensitive to occupancy rate variation. In this context, this research has the potential to help in the creation of the first Brazilian industrial plant dedicated to the recycling of printed circuit boards, as well as to understand the key variables for the processing of these components. Additionally, the project presents the investment necessary for the creation of the plant, being crucial information for potential investors.

<p>Pumped municipal solid waste landfill leachate samples (7 cells from a site in Nebraska, 4 cells from a site in Illinois) have been analyzed for 62 elements using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). A procedure for complete dissolution of solids in the leachate was developed. Complete dissolution aims to reduce material loss in filtration by eliminating the need for filtration, and frees materials entrapped in undissolved solids. The procedure uses centrifugation to separate solid phase matter from the raw sample to maximize the effect of acid, and uses Chloric, Nitric, Fluoric, and Boric acids with microwave digestion to achieve full dissolution. The dissolved solid fraction precipitates yttrium fluoride and some other metals due to over-solubility concentrations; the precipitate is recovered and redissolved for analysis. Platinum, (Post-) Transition, and Lanthanide group metals were positively detected in the landfill leachate. Individual metals from these groups were detected in either/both aqueous or/and solid phases: solid phase metals are usually at least one magnitude of concentration greater than liquid phase metals, unless the solid phase produced no detection of the metal where the liquid phase did. Noteworthy results are: in the solid phase; Al was quantified from 10 to 103 𝜇g/g of solid mass; Sc, Cr, Ti, and Cu were quantified in the solid phase from 1 to 50 𝜇g/g of solid mass; Zr and Eu were quantified from .5 to ~8 𝜇g/g of solid mass. In the liquid phase: Ti, Cr, Li, Cu, As, and Zr were quantified mostly between 10-2 to 10-1 𝜇g/g of liquid mass, but occasionally reach out of those bounds; Al, Sc, Pt, Co, and V were quantified mostly from 10-3 to 10-2 𝜇g/g of solid mass. Solid phase metals were positively detected with a minimum Limit of Detection (LOD) usually around 10-1 𝜇g/g of solid mass, including: In, Ge, Pb, Ru, Sb, Ta, Hf, Bi, Yb, La, Ti, Pd, Lu, Dy, and Tb. Liquid phase metals were positively detected with a minimum LOD usually around 10-5 𝜇g/g of liquid mass, including: Tm, Ge, Au, Pb, Sb, Ta, Hf, Sm, Nb, Ho, Ga, Bi, Yb, Pd, Er, and Cd.</p>

Fluid inclusion and mineralogical features indicative of boiling have been characterized in 855 samples from epithermal precious metals deposits along the Veta Madre at Guanajuato, Mexico. Features associated with boiling that have been identified at Guanajuato include colloform texture silica, plumose texture silica, moss texture silica, ghost-sphere texture silica, lattice-bladed calcite, lattice-bladed calcite replaced by quartz and pseudo-acicular quartz after calcite and coexisting liquid-rich and vapor-rich fluid inclusions. Most samples were assayed for Au, Ag, Cu, Pb, Zn, As and Sb, and were divided into high-grade and low-grade samples based on the gold and silver concentrations. For silver, the cutoff for high grade was 100 ppm Ag, and for gold the cutoff was 1 ppm Au. The feature that is most closely associated with high grades of both gold and silver is colloform texture silica, and this feature also shows the largest difference in grade between the presence or absence of that feature (178.8 ppm Ag versus 17.2 ppm Ag, and 1.1 ppm Au versus 0.2 ppm Au). For both Ag and Au, there is no significant difference in average grade as a function of whether or not coexisting liquid-rich and vapor-rich fluid inclusions are present. The textural and fluid inclusion data obtained in this study were analyzed using the binary classifier within SPSS Clementine. The models that correctly predicted high versus low grade samples most consistently (~70-75% of the tests) for both Ag and Au were the neural network, the C5 decision tree and Quest decision tree models. For both Au and Ag, the presence of colloform silica texture was the variable with the greatest importance, i.e., the variable that has the greatest predictive power. Boiling features are absent or rare in samples collected along a traverse perpendicular to the Veta Madre. This suggests that if an explorationist observes these features in samples collected during exploration that an environment favorable to precious metal mineralization is nearby. Similarly, good evidence for boiling is observed in the deepest levels of the Veta Madre that have been sampled in the mines and drill cores, suggesting that additional precious metal reserves are likely beneath the deepest levels sampled. / Master of Science

The research was conducted as a result of the long standing criticism against undercover operations due to the conduct of informers and agents during these operations. Since both undercover operations and informers are controversial issues it may cause serious judicial problems if the system is not applied correctly. The problem was investigated by means of qualitative research. A thorough literature study and semi-structured interviews were used to gather the required data. Semi-structured interviews were conducted with advocates of the Director of Public Prosecutions Free State and detectives from the Organised Crime Unit of the South African Police Service. It has been found that undercover operations are an effective manner to address organised crime and especially precious metals related crimes. Undercover operations are an excellent barometer to determine the extent of organised crime. It gives investigators a clear view of the compilation of a syndicate and the roles of leaders, runners and associates. Informers are invaluable sources of information. Without the use of informers it will be virtually impossible to engage in undercover operations, since the police will have no intelligence to engage into an investigation of this nature. The implications of the findings are that it is the responsibility of investigators, agents and informers to keep the system transparent, fair and acceptable. Their conduct may never violate their mandate and the boundaries of the investigation. Undercover operations are justified when the system is properly administered, structured, controlled and without bias. / Forensic Investigation / M. Tech. (Forensic Investigation)

The research was conducted as a result of the long standing criticism against undercover operations due to the conduct of informers and agents during these operations. Since both undercover operations and informers are controversial issues it may cause serious judicial problems if the system is not applied correctly. The problem was investigated by means of qualitative research. A thorough literature study and semi-structured interviews were used to gather the required data. Semi-structured interviews were conducted with advocates of the Director of Public Prosecutions Free State and detectives from the Organised Crime Unit of the South African Police Service. It has been found that undercover operations are an effective manner to address organised crime and especially precious metals related crimes. Undercover operations are an excellent barometer to determine the extent of organised crime. It gives investigators a clear view of the compilation of a syndicate and the roles of leaders, runners and associates. Informers are invaluable sources of information. Without the use of informers it will be virtually impossible to engage in undercover operations, since the police will have no intelligence to engage into an investigation of this nature. The implications of the findings are that it is the responsibility of investigators, agents and informers to keep the system transparent, fair and acceptable. Their conduct may never violate their mandate and the boundaries of the investigation. Undercover operations are justified when the system is properly administered, structured, controlled and without bias. / Forensic Investigation / M. Tech. (Forensic Investigation)

Gold Foil Figures or guldgubbar (henceforth GFFs) are precious metal artefacts from the Scandinavian Late Iron Age. This master's essay offers a new approach to GFFs. As opposed to the established understanding of GFFs as representational images with real or mythic referents, belonging to an aristocratic milieu, this essay instead attends to GFFs in terms of their material and Figural traits. The material for this study consists if 42 GFFs from the find site of Västra Vång, Blekinge, Sweden. A comprehensive presentation of this artefact material is a secondary aim of this essay. With the aid of a neomaterialist theoretical apparatus that draws heavily on the work of Gilles Deleuze, Félix Guattari, and Wilhelm Worringer, the 42 GFFs undergo two separate analyses. In the first, the material traits expressed in the sequence of GFF production and deposition is studied in terms of a chaîne opératoire. In the second, I attend to the non-significatory expressive qualities of form and expression, or Figural traits, belonging to these 42 GFFs within the wider artistic milieu of Animal Style Ornamentation. I conclude that GFFs were as a rule artefacts made for purposes of immediate disposal, not display, as a mode of dispersing gold. Västra Vång’s GFFs offer several indications that handling between the cutting operation and deposition was minimal, such as the fresh, unworn edges. The thin, brittle foils are ill suited to display. Approaching the designs on these artefacts as various sets of Figural traits being expressed allows me to contextualise the GFFs within the wider artistic milieu of Animal Style Ornamentation. New territorial rhythms can be established only as certain elements are freed from a settled state, and made to act together with new elements, in new terrains. GFFs bring about new territorial rhythms of form and expression to gold matter, gold made to circulate as it becomes deterritorialised from a monetary function within the Roman economy. A flow of gold is extended as gold is brought to Scandinavia from continental economies. The influx of this flow of gold is not contained to an élite social stratum. Individuals in possession of minute amounts of gold returned to Scandinavia, having acquired gold as payment for involvement in military operations on the continent. This ownership of gold may have hindered their harmonious reintegration into a society based on other economic principles. The GFFs emerge as a vector of dispersing gold. The artistic expression of Figural traits is equally energised by movements of de- and reterritorialisation. Understanding that the Figural traits expressed on the GFFs from Västra Vång are part of a wider artistic milieu of Animal Style Ornamentation, alongside other systematised expressions making up parts of a collective assemblage of enunciation, makes their appearance on artefacts that were deposited immediately upon their manufacture easier to grasp. The particular procedures of miniaturisation allowed for an acceleration of the expression of variation in the conjunction of a flow of artistic expression onto a flow of gold matter. The dispersive handling of gold must be traced to both the material premises and the expressive artistic ones. Gold is not chosen because it is precious, or because of what it connotes, but because it is available, because the artisan smith is attendant to its traits as a metal matter.

Exploring new technologies that can meet the world’s energy demands in an efficient and clean manner is critically important due to the depletion of natural resources and environmental concerns. Dye-sensitized solar cells (DSSCs) are low-cost and clean technology options that use solar energy efficiently and are being intensively studied. How to further reduce the cost of this technology while enhancing device performance is one of the demanding issues for large scale application and commercialization of DSSCs. In this research dissertation, four main contributions are made in this regard with the motivation to reduce further cost of DSSC technology. Firstly, ~10% efficiencies were achieved after developing understanding of key concepts and procedures involved in DSSCs fabrication. These efficiencies were achieved after step-by-step modifications in the DSSC design. Secondly, carbon nanotubes (CNTs) were successfully employed as an alternative to Pt in the counter electrodes of DSSCs. DSSCs fabricated with CNTs were ~86% as efficient as Pt-based cells. Non-aligned CNTs were successfully grown using four different CVD methods and finally, multi-walled vertically aligned CNTs (MW-VACNTs) were synthesized using water-assisted chemical vapor deposition (WA-CVD). Thirdly, carbon derived from pyrolysis of nanocrystalline cellulose (NCC) was successfully employed in counter electrodes of DSSCs instead of Pt. DSSCs with NCC were ~58% as efficient as Pt-based DSSCs. Fourthly, novel organic metal-free dyes were designed and employed instead of commonly used Ru-based dyes. DSSCs with these novel sensitizers were ~62% as efficient as those using the conventional Ru-based dyes. Characterization techniques including current-voltage measurements, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetery (CV), thermogravimetric analysis (TGA), small angle x-ray scattering (SAXS), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) were used.

Dans ce travail nous avons étudié des réactions chimiques sur la surface de deux métaux :le platine et l'or, en utilisant la microscopie ionique à effet de champ électrique (FIM) et la spectrométrie de masse de désorption par champ pulsé (PFDMS). En complément de ces données expérimentales, nous apportons des résultats obtenus par la théorie de la fonctionnelle de la densité (DFT). La taille et la morphologie de nos échantillons font qu’ils sont de bons modèles de grains de phase active dans un catalyseur réel.<p>\ / Doctorat en sciences, Spécialisation chimie / info:eu-repo/semantics/nonPublished

This project deals with historical precious metals price development as gold, silver, platinum and palladium in connection to analysis of the precious metals investment benefits. There are discussed international market prices and retail prices as well. There is also mentioned the issue of price structure from the premium and other costs point of view, including possible risks coupled with investment. Approximated are also basic terms and forms of investment metals, alternative options of precious metals investment as well. The project also includes the issue of tax investment aspects and other advantages connected to it. Further there is indicated medial disinformation criticism and insufficient legal support for customers investing to the precious metals.