909 resultados para Stabilised zirconia


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OBJECTIVES The aim of this prospective cohort trial was to perform a cost/time analysis for implant-supported single-unit reconstructions in the digital workflow compared to the conventional pathway. MATERIALS AND METHODS A total of 20 patients were included for rehabilitation with 2 × 20 implant crowns in a crossover study design and treated consecutively each with customized titanium abutments plus CAD/CAM-zirconia-suprastructures (test: digital) and with standardized titanium abutments plus PFM-crowns (control conventional). Starting with prosthetic treatment, analysis was estimated for clinical and laboratory work steps including measure of costs in Swiss Francs (CHF), productivity rates and cost minimization for first-line therapy. Statistical calculations were performed with Wilcoxon signed-rank test. RESULTS Both protocols worked successfully for all test and control reconstructions. Direct treatment costs were significantly lower for the digital workflow 1815.35 CHF compared to the conventional pathway 2119.65 CHF [P = 0.0004]. For subprocess evaluation, total laboratory costs were calculated as 941.95 CHF for the test group and 1245.65 CHF for the control group, respectively [P = 0.003]. The clinical dental productivity rate amounted to 29.64 CHF/min (digital) and 24.37 CHF/min (conventional) [P = 0.002]. Overall, cost minimization analysis exhibited an 18% cost reduction within the digital process. CONCLUSION The digital workflow was more efficient than the established conventional pathway for implant-supported crowns in this investigation.

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Part II - Christoph Neuenschwander: Language ideologies in the legitimisation of Tok Pisin as a lingua franca Pidgins and Creoles all over the world seem to share common aspects in the historical circumstances of their genesis and evolution. They all emerged in the context of colonialism, in which not only colonisers and colonised, but also the various groups of the colonised population spoke different languages. Pidgins and Creoles, quite simply, resulted from the need to communicate.¬¬ Yet, the degree to which they became accepted as a lingua franca or in fact even as a linguistic variety in its own right, strikingly differs from variety to variety. The current research project focuses on two Pacific Creoles: Tok Pisin, spoken on Papua New Guinea, and Hawai'i Creole English (HCE). Whereas Tok Pisin is a highly stabilised and legitimised variety, used as a lingua franca in one of the most linguistically diverse countries on Earth, HCE seems to be regarded as nothing more than broken English by a vast majority of the Hawai'ian population. The aim of this project is to examine the metalinguistic comments about both varieties and to analyse the public discourses, in which the status of Tok Pisin and HCE were and still are negotiated. More precisely, language ideologies shall be identified and compared in the two contexts. Ultimately, this might help us understand the mechanisms that underlie the processes of legitimisation or stigmatisation. As Laura Tresch will run a parallel research project on language ideologies on new dialects (New Zealand English and Estuary English), a comparison between the findings of both projects may produce even more insights into those mechanisms. The next months of the project will be dedicated to investigating the metalinguistic discourse in Papua New Guinea. In order to collect a wide range of manifestations of language ideologies, i.e. instances of (lay and academic) commentary on Tok Pisin, it makes sense to look at a relatively large period of time and to single out events that are likely to have stimulated such manifestations. In the history of Papua New Guinea - and in the history of Tok Pisin, in particular - several important social and political events concerning the use and the status of the language can be detected. One example might be public debates on education policy. The presentation at the CSLS Winter School 2014 will provide a brief introduction to the history of Tok Pisin and raise the methodological question of how to spot potential sites of language-ideological production.

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Four retrogressive thaw slumps (RTS) located on Herschel Island and the Yukon coast (King Point) in the western Canadian Arctic were investigated to compare the environmental, sedimentological and geochemical setting and characteristics of zones in active and stabilised slumps and at undisturbed sites. In general, the slope, sedimentology and biogeochemistry of stabilised and undisturbed zones differ, independent of their age or location. Organic carbon contents were lower in slumps than in the surrounding tundra, and the density and compaction of slump sediments were much greater. Radiocarbon dating showed that RTS were likely to have been active around 300 a BP and are undergoing a similar period of increased activity now. This cycle is thought to be controlled more by local geometry, cryostratigraphy and the rate of coastal erosion than by variation in summer temperatures.

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Executive Summary: Carbon dioxide capture and storage (CCS) is one option for mitigating atmospheric emissions of carbon dioxide and thereby contributes in actions for stabilization of atmospheric greenhouse gas concentrations. The Bellona Foundation is striving to achieve wide implementation of carbon dioxide (CO2) capture and storage both in Norway and internationally. Bellona considers CCS as the only viable large scale option to close the gap between energy production and demand in an environmentally sound way, thereby ensuring that climate changes and acidification of the oceans due to increased CO2 concentrations in the atmosphere will be stabilised. ff

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En los últimos años, las sociedades industrializadas han tomado una mayor conciencia sobre el problema que suponen las emisiones indiscriminadas de gases de efecto invernadero a la atmósfera. El hormigón, cuyo principal componente es el cemento, es probablemente el material más utilizado en construcción. En la actualidad, las emisiones globales de CO2 debidas a la combustión del CaCO3 del cemento Pórtland representan entre el 5% y el 10% respecto del total. Estos valores son de gran interés si se considera que el compromiso aceptado al firmar el Protocolo de Kioto es de una reducción del 5% antes del año 2020, sobre el total de gases producidos. El principal objetivo del presente trabajo es el estudio microestructural y de los procesos de hidratación de los cementos con adiciones. Para ello se propone contribuir a la investigación sobre nuevos productos cementicios basados en micropartículas esféricas vítreas que pueden adicionarse al cemento antes del proceso de amasado. Los resultados obtenidos se han contrastado con las adiciones convencionales de más uso en la actualidad. El nuevo material basa su composición en la química del aluminio y el silicio. Al disminuir la cantidad de CaCO3, se contribuye al desarrollo sostenible y a la reducción de emisiones de CO2. La patente creada por el Grupo Cementos Pórtland Valderrivas (GCPV), describe el proceso de producción de las cemesferas (WO 2009/007470, 2010). Los productos que forman la materia prima para la elaboración de las cemesferas son arcillas, calizas, margas o productos o subproductos industriales, que tras su molienda, son fundidos mediante un fluido gaseoso a elevada temperatura (entre 1250ºC y 1600ºC). Este proceso permite obtener un producto final en forma esférica maciza o microesfera, que tras estabilizarse mediante un enfriamiento rápido, consigue una alta vitrificación idónea para su reactividad química, con una mínima superficie específica en relación a su masa. El producto final obtenido presenta prácticamente la finura requerida y no precisa ser molido, lo que reduce las emisiones de CO2 por el ahorro de combustible durante el proceso de molienda. El proceso descrito permite obtener un amplio abanico de materiales cementantes que, no solo pueden dar respuesta a los problemas generados por las emisiones de CO2, sino también a la disponibilidad de materiales en países donde hasta el momento no se puede fabricar cemento debido a la falta de calizas. Complementariamente se ha optimizado el método de cálculo del grado de hidratación a partir de los resultados del ensayo de ATD-TG en base a los modelos de cálculo de Bhatty y Pane. El método propuesto permite interpretar el comportamiento futuro del material a partir de la interpolación numérica de la cantidad de agua químicamente enlazada. La evolución del grado de hidratación tiene una relación directa con el desarrollo de la resistencia mecánica del material. Con el fin de caracterizar los materiales de base cemento, se ha llevado a cabo una amplia campaña experimental en pasta de cemento, mortero y hormigón. La investigación abarca tres niveles: caracterización microestructural, macroestructural y caracterización del comportamiento a largo plazo, fundamentalmente durabilidad. En total se han evaluado ocho adiciones diferentes: cuatro adiciones convencionales y cuatro tipos de cemesferas con diferente composición química. Los ensayos a escala microscópica comprenden la caracterización química, granulométrica y de la superficie específica BET de los materiales anhidros, análisis térmico diferencial y termogravimétrico en pasta de cemento y mortero, resonancia magnética de silicio en pasta de cemento, difracción de rayos X de los materiales anhidros y de las probetas de pasta, microscopía electrónica de barrido con analizador de energía dispersiva por rayos X en pasta y mortero, y porosimetría por intrusión de mercurio en mortero. La caracterización macroscópica del material comprende ensayos de determinación del agua de consistencia normal y de los tiempos de inicio y fin de fraguado en pasta de cemento, ensayos de resistencia mecánica a flexión y compresión en probetas prismáticas de mortero, y ensayos de resistencia a compresión en probetas de hormigón. Para caracterizar la durabilidad se han desarrollado ensayos de determinación del coeficiente de migración de cloruros y ensayos de resistividad eléctrica en probetas de mortero. Todos los ensayos enumerados permiten clarificar el comportamiento de las cemesferas y compararlo con las distintas adiciones de uso convencional. Los resultados reflejan un buen comportamiento resistente y durable de los materiales con adición de cemesferas. La caracterización microscópica refleja su relación con las propiedades mesoscópicas y permite comprender mejor la evolución en los procesos de hidratación de las cemesferas. In recent years industrialised societies have become increasingly aware of the problem posed by indiscriminate emission of greenhouse gases into the atmosphere. Concrete, with a main component being cement, is arguably the most widely used construction material. At present, global emissions of CO2 due to the combustion of CaCO3 from Portland cement represent between 5% and 10% of the total. If the requirement of the Kyoto Protocol of a reduction of 5% of the total gas produced before 2020 is considered, then such values are of significant interest. The main objective of this work is the assessment of the microstructure and the hydration processes of cements with additions. Such an examination proposes research into new cementitious products based on vitreous spherical microparticles that may be added to the cement before the mixing process. The results are compared with the most commonly used conventional additions. The new material bases its composition on the chemistry of aluminium and silicates. By decreasing the amount of CaCO3, it is possible both to contribute to sustainable development and reduce CO2 emissions. The patent created by Grupo Cementos Portland Valderrivas (GCPV) describes the production process of microspheres (WO 2009/007470, 2010). The products that form the raw material for manufacture are clays, lime-stone, marl and industrial products or by-products that melt after being ground and fed into a gaseous fluid at high temperatures (1250°C and 1600°C). This process allows the obtaining of a product with a solid-spherical or micro-spherical shape and which, after being stabilised in a solid state by rapid cooling, obtains a high vitrification suitable for chemical reactivity, having a minimal surface in relation to its mass. Given that the final product has the fineness required, it prevents grinding that reduces CO2 emissions by saving fuel during this process. The process, which allows a wide range of cementitious materials to be obtained, not only addresses the problems caused by CO2 emissions but also enhances the availability of materials in countries that until the time of writing have not produced cement due to a lack of limestone. In addition, the calculation of the degree of hydration from the test results of DTA-TG is optimised and based on Bhatty and Pane calculation models. The proposed method allows prediction of the performance of the material from numerical interpolation of the amount of chemically bound water. The degree of hydration has a direct relationship with the development of material mechanical strength. In order to characterise the cement-based materials, an extensive experimental campaign in cement paste, concrete and mortar is conducted. The research comprises three levels: micro-structural characterisation, macro-structural and long-term behaviour (mainly durability). In total, eight additions are assessed: four conventional additions and four types of microspheres with different chemical compositions. The micro-scale tests include characterisation of chemical composition, particle size distribution and the BET specific surface area of anhydrous material, differential thermal and thermogravimetric analysis in cement paste and mortar, silicon-29 nuclear magnetic resonance in cement paste, X-ray diffraction of the anhydrous materials and paste specimens, scanning of electron microscopy with energy dispersive X-ray analyser in cement paste and mortar, and mercury intrusion porosimetry in mortar. The macroscopic material characterisation entails determination of water demand for normal consistency, and initial and final setting times of cement paste, flexural and compressive mechanical strength tests in prismatic mortar specimens, and compressive strength tests in concrete specimens. Tests for determining the chloride migration coefficient are performed to characterise durability, together with electrical resistivity tests in mortar specimens. All the tests listed allow clarification of the behaviour of the microspheres and comparison with the various additions of conventional use. The results show good resistance and durable behaviour of materials with a microsphere addition. Microscopic characterisation reflects their relationship with mesoscopic properties and provides insights into the hydration processes of the microspheres.

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En este trabajo, materiales de tipo alúmina/Y-TZP (ZrO2 tetragonal, estabilizada con 3 mol. % Y2O3), como sistema cerámico popular por sus mejoradas propiedades mecánicas en comparación con las cerámicas de alúmina puras, han sido estudiados en términos de propiedades mecánicas y tensiones residuales. El novedoso método de colado en cinta, consistente en el apilamiento de cintas de cerámica verde a temperatura ambiente y el uso de bajas presiones, se ha escogido para la presente investigación con el fin de poder aprovechar al máximo el futuro desarrollo de materiales laminados de alúmina-óxido de circonio. Se han determinado las propiedades de los materiales obtenidos por este nuevo método de procesamiento comparándolas con las de los materiales obtenidos por “slip casting”, con el fin de analizar si el método propuesto afecta a la microestructura y, por tanto, a las propiedades mecánicas y tensiones residuales propias de estos materiales. Para analizar la idoneidad del proceso de fabricación, utilizado para evitar la presencia de discontinuidades en las intercaras entre las láminas así como otros fenómenos que puedan interferir con las propiedades mecánicas, se estudiaron materiales cerámicos con la misma composición en cintas. Por otra parte también se analizó el efecto de la adición de óxido de circonio sobre la aparición de tensiónes residuales en cerámicas Al2O3/Y-TZP, teniendo en cuenta su notable influencia sobre las propiedades microestructurales y mecánicas de los materiales, así como el requisito de co-sinterización de capas con diferentes materiales compuestos en materiales laminados. La caracterización del material incluye la determinación de la densidad, el análisis de la microestructura, la obtención de las propiedades mecánicas (módulo de elasticidad, dureza, resistencia a la flexión y tenacidad de fractura) así como de las tensiones residuales. En combinación con otros métodos de medida tradicionales, la nanoindentación también se empleó como una técnica adicional para la medida del módulo de elasticidad y de la dureza. Por otro lado, diferentes técnicas de difracción con neutrones, tanto las basadas en longitud de onda constante (CW) como en tiempo de vuelo (TOF), han sido empleadas para la medición fiable de la deformación residual a través del grosor en muestras a granel. Las tensiones residuales fueron determinadas con elevada precisión, aplicando además métodos de análisis apropiados, como por ejemplo el refinamiento de Rietveld. Las diferentes fases en cerámicas sinterizadas, especialmente las de zirconia, se examinaron con detalle mediante el análisis de Rietveld, teniendo en cuenta el complicado polimorfismo del Óxido de Zirconio (ZrO2) así como las posibles transformaciones de fase durante el proceso de fabricación. Los efectos del contenido de Y-TZP en combinación con el nuevo método de procesamiento sobre la microestructura, el rendimiento mecánico y las tensiones residuales de los materiales estudiados (Al2O3/Y-TZP) se resumen en el presente trabajo. Finalmente, los mecanismos de endurecimiento, especialmente los relacionados con las tensiones residuales, son igualmente discutidos. In present work, Alumina/Y-TZP (tetragonal ZrO2 stabilized with 3 mol% Y2O3) materials, as an popular ceramic system with improved mechanical properties compared with the pure alumina ceramics, have been studied in terms of mechanical properties and residual stresses. The novel tape casting method, which involved the stacking of green ceramics tapes at room temperature and using low pressures, is selected for manufacturing and investigation, in order to take full advantage of the future development of alumina-zirconia laminated materials. Features of materials obtained by the new processing method are determined and compared with those of materials obtained by conventional slip casting in a plaster mold, in order to study whether the proposed method of processing affects microstructure and thereby the mechanical properties and residual stresses characteristics of materials. To analyse the adequacy of the manufacturing process used to avoid the presence of discontinuities at the interfaces between the sheets and other phenomena that interfere with the mechanical properties, ceramic materials with the same composition in tapes were investigated. Moreover, the effect of addition of zirconia on residual stress development of Al2O3/Y-TZP ceramics were taken into investigations, considering its significantly influence on the microstructure and mechanical properties of materials as well as the requirement of co-sintering of layers with different composites in laminated materials. The characterization includes density, microstructure, mechanical properties (elastic modulus, hardness, flexure strength and fracture toughness) and residual stresses. Except of the traditional measurement methods, nanoindentation technique was also used as an additional measurement of the elastic modulus and hardness. Neutron diffraction, both the constant-wavelength (CW) and time-of-flight (TOF) neutron diffraction techniques, has been used for reliable through-thickness residual strain measurement in bulk samples. Residual stresses were precisely determined combined with appropriate analysis methods, e.g. the Rietveld refinement. The phase compositions in sintered ceramics especially the ones of zirconia were accurately examined by Rietveld analysis, considering the complex polymorph of ZrO2 and the possible phase transformation during manufacturing process. Effects of Y-TZP content and the new processing method on the microstructure, mechanical performance and residual stresses were finally summarized in present studied Al2O3/Y-TZP materials. The toughening mechanisms, especially the residual stresses related toughening, were theoretically discussed.

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We have used DNase I footprinting to examine the interaction of several triplex-binding ligands with antiparallel TG- and AG-containing triplexes. We find that although a 17mer TG-containing oligonucleotide on its own fails to produce a footprint at concentrations as high as 30 µM, this interaction can be stabilised by several ligands. Within a series of disubstituted amidoanthraquinones we find that the 2,7- regioisomer affords the best stabilisation of this TG triplex, though the 1,8- isomer also stabilises this interaction to some extent. By contrast the 1,5- and 2,6- regioisomers show no interaction with TG triplexes. Similar studies with a 13mer AG-containing oligonucleotide show the opposite pattern of stabilisation: the 2,6- and 1,5- isomers stabilise this triplex, but the 2,7- and 1,8-compounds do not. The polycyclic compound BePI strongly stabilises TG- but not AG-containing triplexes, while a substituted naphthylquinoline interacts with both antiparallel triplex motifs.

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A presente Dissertação relata a síntese e o estudo conformacional das α-fenilseleno-α-dietóxifosforilacetofenonas para-substituídas p-X-Φ-C(O)CH[SeΦ][P(O)(OEt2] (X=OMe 1, Me 2, H 3, F 4, Cl 5, Br 6 e NO2 7) através da banda de estiramento da carbonila no infravermelho, em solventes de polaridade crescente apoiado por cálculos ab initio HF/6-3IG**. A comparação entre a freqüência e a intensidade relativa dos componentes do dubleto, para os derivados 6 e 7, e do singleto para os derivados 1-5, no solvente apolar tetracloreto de carbono, e dos componentes do dubleto, nos solventes de polaridade crescente (clorofórmio, diclorometano e acetonitrila), para os derivados 1-7, com os dados do cálculo ab initio de 3 (composto de referência), indicou que ambas as conformações estáveis (g1 e g2) apresentam a ligação C-Se na geometria anti-clinal (gauche) em relação à carbonila (C=O), enquanto que a ligação C-P assume uma geometria sin-periplanar (cis) em relação à carbonila. A análise dos contatos interatômicos de átomos relevante em comparação com a soma de seus raios de van der Waals, indicou que ambas as conformações g1 e g2 são fortemente estabilizadas pelo sinergismo das interações orbitalares e eletrostáticas π*(CO) / nSe e Oδ-[CO].....Pδ+[PO]. Analogamente, as interações mais fracas Oδ-[OR]..... Cδ+[CO], 0-Hδ+[SeΦ]....Oδ-[PO] e 0-Hδ+[ΦC(O)]....Oδ-[CO] estabilizam as conformações g1 e g2, aproximadamente na mesma extensão. No entanto, somente a conformação g1 é estabilizada pela interação eletrostática (ligação de hidrogênio) Hδ+[α-CH].....Oδ-[OR], enquanto que sómente a conformação g2 é desestabilizada pelo Efeito de Campo Repulsivo entre os dipolos Cδ+=.Oδ- e Pδ+-ORδ- Assim sendo, pode-se concluir que no dubleto de VCO no IV, o componente de maior freqüência e de menor intensidade corresponde à conformação menos estável g2 (do cálculo) enquanto que o componente de menor freqüência e mais intenso corresponde à conformação mais estável g1 (do cálculo). Estes dados estão de pleno acordo com os deslocamentos de freqüência mais negativos da carbonila (ΔVCO) do confôrmero mais estável g1 em relação ao menos estável g2.

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Nesse trabalho foi proposto investigar a estabilidade de fases do sistema zircônia-escândia (ScSZ) por meio do estudo termodinâmico de nanopartículas, na faixa de 0 a 20% em mol de Sc2O3, e a partir da introdução de um segundo aditivo (Dy2O3 e Nb2O5) ao ZrO2 contendo 10% em mol de Sc2O3 (10ScSZ). A estabilidade de fases do ScSZ foi avaliada com base em dados termodinâmicos determinados pelas técnicas de microcalorimetria de adsorção de água e calorimetria de dissolução à alta temperatura. As soluções sólidas foram sintetizadas pelo método de coprecipitação de hidróxidos. Dados termodinâmicos foram determinados para as formas polimórficas encontradas (monoclínica, tetragonal, cúbica, romboédrica β e γ) por difração de raios X no ScSZ. Esse trabalho resultou no diagrama de fases em nanoescala de tamanho de partícula-composição. Os efeitos produzidos pela introdução de aditivos na matriz de 10ScSZ foram investigados visando obter a possível estabilização da estrutura cúbica (c) e a supressão da transformação de fase c-β, característica do sistema binário. As composições foram sintetizadas por coprecipitação de hidróxidos e por reações em estado sólido para fins comparativos. Os materiais foram sinterizados convencionalmente e por sinterização assistida por campo elétrico. A estabilização completa da fase cúbica ocorreu a partir de teores molares de 1% de Dy2O3 e 0,5% de Nb2O5. O menor teor de Nb2O5 necessário para a estabilização da fase foi atribuído à provável formação da fase líquida durante a sinterização e ao menor tamanho do íon Nb5+. Os resultados de difratometria de raios X em alta temperatura e análise térmica mostraram que houve supressão da transição c-β. As amostras contendo 0,5% mol de Nb2O5 apresentaram valores de condutividade iônica similares aos do 10ScSZ sem aditivos em uma ampla faixa de temperatura com elevada estabilidade em um período de 170 h a 600 °C.

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CuO/ceria-zirconia catalysts have been prepared, deeply characterised (N2 adsorption–desorption isotherms at −196 °C, XRD, Raman spectroscopy, XPS, TEM and H2-TPR) and tested for NO oxidation to NO2 in TPR conditions, and for soot combustion at mild temperature (400 °C) in a NOx/O2 stream. The behaviour has been compared to that of a reference Pt/alumina commercial catalyst. The ceria-zirconia support was prepared by the co-precipitation method, and different amounts of copper (0.5, 1, 2, 4 and 6 wt%) were loaded by incipient wetness impregnation. The results revealed that copper is well-dispersed onto the ceria-zirconia support for the catalysts with low copper loading and CuO particles were only identified by XRD in samples with 4 and 6% of copper. A very low loading of copper increases significantly the activity for the NO oxidation to NO2 with regard to the ceria-zirconia support and an optimum was found for a 4% CuO/ceria-zirconia composition, showing a very high activity (54% at 348 °C). The soot combustion rate at 400 °C obtained with the 2% CuO/ceria-zirconia catalyst is slightly lower to that of 1% Pt/alumina in terms of mass of catalyst but higher in terms of price of catalyst.

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This work presents a comparative study between the catalytic performance of the 2% CuO/ceria-zirconia powder catalyst and the same catalyst supported on silicon carbide DPF (Diesel Particulate Filter) towards NO oxidation reaction and soot combustion reaction. The ceria-zirconia catalyst was prepared by the co-precipitation method and 2 wt% copper was incorporated by the incipient wetness impregnation method. The catalyst was incorporated onto the ceramic support using a simple and organic solvent-free procedure by a simply dipping the DPF into an aqueous solution of the catalyst. The powder catalyst has been characterized using N2 adsorption at −196 °C, XRD and Raman Spectroscopy; whereas the catalytic coating morphology has been evaluated by SEM and the mechanical stability by an adherence test. Both catalyst configurations were tested for NO oxidation to NO2 and for soot combustion under NOx/O2. The results revealed that incorporation of the very active copper/ceria-zirconia catalyst onto SiC-DPF has been successfully achieved by a simple coating procedure. Furthermore, the catalytic coating has shown suitable mechanical, chemical and thermal stability. A satisfactory catalytic performance of the catalytic-coated filter was reached towards the NO oxidation reaction. Moreover, it was proved that the catalytic coating is stable and the corresponding coated DPF can be reused for several cycles of NO oxidation without a significant decrease in its activity. Finally, it was verified that the loose-contact mode is a good choice to simulate the catalytic performance of this active phase in a real diesel particulate filter.

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The issue: The European Union's emissions trading system (ETS), introduced in 2005, is the centerpiece of EU decarbonisation efforts and the biggest emissions trading scheme in the world. After a peak in May 2008, the price of ETS carbon allowances started to collapse, and industry, civil society and policymakers began to think about how to ‘repair the ETS’. However, the ETS is an effective and efficient tool to mitigate greenhouse gas emissions, and although prices have not been stable, it has evolved to cover more sectors and greenhouse gases, and to become more robust and less distorting. Prices are depressed because of an interplay of fundamental factors and a lack of confidence in the system. Policy challenge The ETS must be stabilised by reinforcing the credibility of the system so that the use of existing low-carbon alternatives (for example burning gas instead of coal) is incentivised and investment in low-carbon assets is ensured. Further-more, failure to reinvigorate the ETS might compromise the cost-effective synchronisation of European decarbonisation efforts across sectors and countries. To restore credibility and to ensure long-term commitment to the ETS, the European Investment Bank should auction guarantees on the future emission allowance price.This will reduce the risk for low-carbon investments and enable stabilisation of the ETS until a compromise is found on structural measures to reinforce it in order to achieve the EU's long-term decarbonisation targets.

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The political crisis in Ukraine, particularly the bloodshed seen on 18–20 February and the subsequent Russian intervention in Crimea, has sparked fears of another possible wave of immigrants heading to the EU. However, the country was partially politically stabilised (at least in its central and western parts), and this has made the scenario of a mass migration of people from Ukraine rather unlikely. If there is no civil war in Ukraine, any further development of the political situation in Ukraine may have only an indirect impact on the actual migration. Should the political instability continue, the Ukrainian economy remain in recession while jobs are available for Ukrainian immigrants in the EU, then an increase in the migration of Ukrainian citizens to the EU, including Poland, would be possible. In the short term there may be two characteristic groups of immigrants: (1) young people who will attempt to leave Ukraine for good due to the lack of job opportunities; (2) circulating migrants, mainly from western Ukraine, who will be looking for temporary jobs. Only if the economic downturn trend and political turmoil in Ukraine continues for a longer time, will settlement migration increase.

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Following several years of political turmoil triggered by constitutional reform (a shift from a presidential to a semi-presidential system) and electoral reshuffles (parliamentary elections in 2012; presidential elections in 2013), the political situation in Georgia has stabilised: key posts in the country are now in the hands of democratically elected members of the Geor-gian Dream coalition. Despite its mosaic-like structure and internaltensions, Georgian Dream remains strong and enjoys high levels of public support. This puts it in good stead to play a central role in Georgian politics in the foreseeable future, including securing victory in the local government elections scheduled for June. However, local billionaire Bidzina Ivanishvili does not currently hold a political office - despite the fact that he is the founder, sponsor and undisputed leader of the coalition, as well as former prime minister and the most popular public figure in Georgia (besides Patriarch Ilia II). This raises several questions, for example: Who is really at the helm of the Georgian state? What is the lon-g-term vision of the current government? The past achievements of the politically heterogeneo-us Georgian Dream - dominated by Mr Ivanishvili - offer little help in answering these questions. In addition to a series of challenges on the domestic front, the new Georgian leadership is also facing strategic geopolitical challenges, compounded by the current conflict in Ukraine. These include the future of Georgia’s relations with the West (including the process of EU and NATO integration) and with Russia (in response to repeated attempts to re-integrate the post-Soviet republics). The scale and dynamism of the changes in both the geopolitical order in the post-Soviet region and in the relations between Russia and the West are causing further questions to be raised about their impact on the position of the Georgian political elite and about their consequences for the entire country.