Effect of surface and heat treatments on the biaxial flexural strength and phase transformation of a y-tzp ceramic

To evaluate the effect of grinding and airborne-particle abrasion on the biaxial flexural strength (BFS) and phase transformation of a Y-TZP ceramic, and examine whether sintering the veneering porcelain renders the previous heat treatment recommended by the manufacturer unnecessary. Materials and Methods: Lava zirconia specimens (N = 108) were obtained with the following dimensions: 14.0 mm diameter × 1.3 mm thickness (n = 36) and 14.0 mm × 1.6 mm (n = 72). The thicker specimens were ground with diamond burs under irrigation and received (heat-treated groups) or not (non-heat-treated groups) a heat treatment (1000°C for 30 min) prior to the four firing cycles applied to simulate the sintering of the veneering porcelain. All specimens were air abraded as follows (n = 12): 1) 30-μm silica-modified Al2O3 particles (Rocatec Soft); 2) 110-μm silica-modified Al2O3 particles (Rocatec Plus); and 3) 120-μm Al2O3 particles, followed by Rocatec Plus. Three specimens of each group were analyzed by x-ray diffraction (XRD) to assess the monoclinic phase content (%). The BFS test was performed in a mechanical testing machine (Instron 8874). Data (MPa) were analyzed by two-way ANOVA (grinding × airborne-particle abrasion and heat treatment × airborne-particle abrasion) and Tukey's post-hoc test (α = 0.05). The strength reliability was analyzed using the Weibull distribution. Results: Grinding significantly decreased the BFS of the non-heat-treated groups (p < 0.01). Within the ground groups, the previous heat treatment did not influence the BFS (p > 0.05). Air abrasion only influenced the BFS of the ground/heat-treated groups (p < 0.01). For the non-heat-treated groups, the grinding did not decrease the Weibull modulus (m), but it did decrease the characteristic strength (σ0). For Rocatec Soft and 120-μm Al2O3 particles + Rocatec Plus, the heat-treated groups presented lower m and higher σ0 than the ground/non-heat-treated groups. The independent variables did not seem to influence phase transformation. Air-abraded surfaces presented higher monoclinic zirconia content than the as-sintered and ground surfaces, which exhibited similar content. Conclusion: Even under irrigation, grinding compromised the Y-TZP ceramic strength. The sintering of the veneering porcelain rendered the previous heat treatment recommended by the manufacturer unnecessary. Airborneparticle abrasion influenced the strength of heat-treated zirconia.

O centenário da ferrovia brasileira (1954): ensaio sobre a elabo-ração da memória ferroviária no Brasil

In 1954, it was celebrated the centenary of railways in Brazil. The date refers to the first section of 14.5 km of railway in Brazil (30/04/1854), in Rio de Janeiro, between Mauá and Fragoso, of the Petropolis Railway Company (Estrada de Ferro Petrópolis). Some of the texts and commemorative events indicated the symbolic values that the railroad took in the Brazilian history. Firstly, on 30.04.1954, the railway section Mauá-Fragoso and steam locomotive “Baroness” (the first used on the track) were declared national monuments(Decree No. 35,447-A, April 30, 1954). Secondly, some entities (Clube de Engenharia, Conselho Nacional de Geografia, Ministério da Viação e Obras Públicas) highlighted the importance of celebrating the Brazilian railway history and its historical significance, economic and geographical. For this, some events was occurred (the commemoration of one hundred years in Rio de Janeiro and Recife on 30.04.1954). Among the texts wrought produced, we highlight the text I Centenary of Brazilian Railroad (1954), released by the Brazilian Institute of Geography and Statistics (Instituto Brasileiro de Geografia e Estatística), and the National Council of Geography (Conselho Nacional de Geografia). The emphasis given to the railway refersto the geographical perspective (territorial expansion), but also makes mention of the Barãode Mauá, the founder of Petropolis Railway Company. We aim to understand the celebration from evocations about the Brazilian railroad history and some ideas that is assigned to the railway (and the Barãode Mauá), and railway heritage (the track and the locomotive “Baroneza”). On basis of this review will seek to understand how it was reconceived the railroad memory in view of these values and material elements.

Caracterização microestrutural e crescimento subcrítico de trincas em cerâmicas odontológicas

Pós-graduação em Odontologia Restauradora - ICT

Impacto da energia de micro-ondas na sinterização da zircônia odontológica

Pós-graduação em Odontologia Restauradora - ICT

Efeitos imediatos e tardios da imersão em água pós-exercício: uma revisão sistemática e um ensaio clínico randomizado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos do treinamento resistido na síndrome metabólica: uma revisão sistemática com meta-análise e um ensaio clínico randomizado

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Exercício físico resistido em pacientes com doença renal crônica em hemodiálise: ensaio clínico randomizado controlado

Pós-graduação em Fisioterapia - FCT

Efeito da infiltração de sílica pelo método sol-gel na resistência à flexão de bicamadas de porcelana e Y-TZP

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A pesquisa em psicologia: ensaio sobre a Psicologia enquanto ciência, a pesquisa qualitativa e o uso da entrevista como principal instrumento de coleta de dados

For constituting itself a science, Psychology has coursed along way. From the time he was considered a Philosophy’s discipline until to be recognized as a legitimate science, Psychology had to devoteto the definition of its object of study, the development and refinement of theoretical-methodological frameworks and, in particular, to consolidation process of their research strategies and knowledge construction. Therefore, in order to regard the demands of the classical scientific paradigm, which is very influenced by Positivism, Psychology made use, initially, of quantitative methodology and laboratory research. This article presents some of the process of identity construction of Psychology as a science, focusing on its transition path between the quantitativist paradigm of scientific knowledge production to the qualitativist paradigm, until that is more commonly practiced nowadays: the collaborative use of these methodological strategies. For presenting the qualitative researching Psychology, we discussed, beyond its proposal and differentiation elements in relation to quantitative research, the different methods used for this mode and, in particular, the interview - which is considered the main way of data collection in surveys conducted by psychologists and, therefore, it is an important element the process of knowledge building that science, in addition to being the most qualified space for dialogue between there searcher and the research subject.

Dispositivo estratégico, resistência e relações de poder: um ensaio sobre a identidade do Centro de Educação Matemática (CEM) e seu papel na (E)educação (M)matemática brasileira

This paper presents some results of the investigation on the Mathematical Education Centre (CEM), a group of mathematics teachers’ educators in São Paulo, Brazil, acting mainly between 1984 and 1997. The essay, marked by an effort to constitute the identity of the CEM based on Foucault, assumes that the identity constitution process is not about what CEM is or was, but mainly about a set of possibilities of apprehending it from its historically contextualized strategies and initiatives. In this Foucauldian reading, which brings about concepts such as "strategic device", "resistance" and "power relations", the CEM constitution appears while it creates conditions for the constitution of Brazilian modern mathematical education.

As matemáticas modernas: um ensaio sobre os modos de produção de significado ao(s) movimento(s) no ensino primário brasileiro

The main goal of this paper is to discuss the production of meaning of the Modern Math Movement. The main sources were data available in school archives and interviews with former teachers that we use in order to focus on the diversity of perspectives -that complement it or oppose it-, which comes up when teachers refer to the Movement. Using this process of signification, teachers whether accept it, invalidate it or adapt it to guidelines imposed to them in their teaching activities. We establish a methodology by following the premises of Oral History to gather oral testimonies. The theoretical foundations in which this article is written are the guidelines of Paul Ricoeur’s Hermeneutics, John Thompson’s Depth Hermeneutics and Bolívar’s narrative analysis.