69 research outputs found

    Low (and negative) thermal expansion Al2TiO5 materials and Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4 composite materials. Processing, initial zircon proportion effect, and properties

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    Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (αapp from −1.5 to 2.5 × 10−6 °C−1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.Fil: Violini, María Agustina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; ArgentinaFil: Hernández, Maria Florencia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; ArgentinaFil: Gauna, Matias Roberto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Suarez, Gustavo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; ArgentinaFil: Conconi, M.S.. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; ArgentinaFil: Rendtorff Birrer, Nicolás Maximiliano. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin

    Low (and negative) thermal expansion Al<SUB>2</SUB>TiO<SUB>5</SUB> materials and Al<SUB>2</SUB>TiO<SUB>5</SUB> - 3Al<SUB>2</SUB>O<SUB>3</SUB>.2SiO<SUB>2</SUB> - ZrTiO<SUB>4</SUB> composite materials : Processing, initial zircon proportion effect, and properties

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    Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (αapp from −1.5 to 2.5×10−6 °C−1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.Centro de Tecnología de Recursos Minerales y Cerámic

    Low (and negative) thermal expansion Al<SUB>2</SUB>TiO<SUB>5</SUB> materials and Al<SUB>2</SUB>TiO<SUB>5</SUB> - 3Al<SUB>2</SUB>O<SUB>3</SUB>.2SiO<SUB>2</SUB> - ZrTiO<SUB>4</SUB> composite materials : Processing, initial zircon proportion effect, and properties

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    Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (αapp from −1.5 to 2.5×10−6 °C−1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.Centro de Tecnología de Recursos Minerales y Cerámic

    Low (and negative) thermal expansion Al<SUB>2</SUB>TiO<SUB>5</SUB> materials and Al<SUB>2</SUB>TiO<SUB>5</SUB> - 3Al<SUB>2</SUB>O<SUB>3</SUB>.2SiO<SUB>2</SUB> - ZrTiO<SUB>4</SUB> composite materials : Processing, initial zircon proportion effect, and properties

    Get PDF
    Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (αapp from −1.5 to 2.5×10−6 °C−1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.Centro de Tecnología de Recursos Minerales y Cerámic

    Transcathether aortic valve implantation with the new repositionable self-expandable Evolut R versus CoreValve system: A case-matched comparison

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    Background: Despite promising results following transcatheter aortic valve implantation (TAVI), several relevant challenges still remain. To overcome these issues, new generation devices have been developed. The purpose of the present study was to determine whether TAVI with the new self-expanding repositionable Evolut R offers potential benefits compared to the preceding CoreValve, using propensity matching. Methods: Between June 2007 and November 2015, 2148 consecutive patients undergoing TAVI either CoreValve (n = 1846) or Evolut R (n = 302) were prospectively included in the Italian TAVI ClinicalService® project. For the purpose of our analysis 211 patients treated with the Evolut R were matched to 211 patients treated with the CoreValve. An independent core laboratory reviewed all angiographic procedural data and an independent clinical events committee adjudicated all events. Results: Patients treated with Evolut R experienced higher 1-year overall survival (log rank test p = 0.045) and a significantly lower incidence of major vascular access complications, bleeding events and acute kidney injury compared to patients treated with the CoreValve. Recapture manoeuvres to optimize valve deployment were performed 44 times, allowing a less implantation depth for the Evolut R. As a consequence, the rate of more than mild paravalvular leak and new permanent pacemaker was lower in patients receiving the Evolut R. Conclusion: In this matched comparison of high surgical risk patients undergoing TAVI, the use of Evolut R was associated with a significant survival benefit at 1. year compared with the CoreValve. This was driven by lower incidence of periprocedural complications and higher rates of correct anatomic positioning

    Meta-analysis of randomized trials on drug-eluting stents vs. bare-metal stents in patients with acute myocardial infarction

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    Aims To compare the efficacy and safety of drug-eluting stents vs. bare-metal stents in patients with acute ST-segment elevation myocardial infarction. Methods and results We performed a meta-analysis of eight randomized trials comparing drug-eluting stents (sirolimus-eluting or paclitaxel-eluting stents) with bare-metal stents in 2786 patients with acute ST-segment elevation myocardial infarction. All patients were followed up for a mean of 12.0-24.2 months. Individual data were available for seven trials with 2476 patients. The primary efficacy endpoint was the need for reintervention (target lesion revascularization). The primary safety endpoint was stent thrombosis. Other outcomes of interest were death and recurrent myocardial infarction. Drug-eluting stents significantly reduced the risk of reintervention, hazard ratio of 0.38 (95% CI, 0.29-0.50), P < 0.001. The overall risk of stent thrombosis: hazard ratio of 0.80 (95% CI, 0.46-1.39), P = 0.43; death: hazard ratio of 0.76 (95% CI, 0.53-1.10), P = 0.14; and recurrent myocardial infarction: hazard ratio of 0.72 (95% CI, 0.48-1.08, P = 0.11) was not significantly different for patients receiving drug-eluting stents vs. bare-metal stents. Conclusion The use of drug-eluting stents in patients with acute ST-segment elevation myocardial infarction is safe and improves clinical outcomes by reducing the risk of reintervention compared with bare-metal stent

    A Qualitative Exploration of the Use of Contraband Cell Phones in Secured Facilities

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    Offenders accepting contraband cell phones in secured facilities violate state corrections law, and the possession of these cell phones is a form of risk taking behavior. When offenders continue this risky behavior, it affects their decision making in other domains where they are challenging authorities; and may impact the length of their incarceration. This qualitative phenomenological study examined the lived experience of ex-offenders who had contraband cell phones in secured correctional facilities in order to better understand their reasons for taking risks with contraband cell phones. The theoretical foundation for this study was Trimpop\u27s risk-homeostasis and risk-motivation theories that suggest an individual\u27s behaviors adapt to negotiate between perceived risk and desired risk in order to achieve satisfaction. The research question explored beliefs and perceptions of ex-offenders who chose to accept the risk of using contraband cell phones during their time in secured facilities. Data were collected anonymously through recorded telephone interviews with 8 male adult ex-offenders and analyzed using thematic content analysis. Findings indicated participants felt empowered by possession of cell phones in prison, and it was an acceptable risk to stay connected to family out of concern for loved ones. The study contributes to social change by providing those justice system administrators, and prison managers responsible for prison cell phone policies with more detailed information about the motivations and perspectives of offenders in respect to using contraband cell phones while imprisoned in secured facilities
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