Al2O3/ZrO2/Y3Al5O12 composites. A high-temperature mechanical characterization

An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix. The high temperature mechanical properties were investigated by four-point bending tests up to 1500 °C, and the grain size stability was assessed by observing the microstructural evolution of the samples heat treated up to 1700 °C. Dynamic indentation measures were performed on as-sintered and heat-treated Al2O3/ZrO2/YAG samples in order to evaluate the micro-hardness and elastic modulus as a function of re-heating temperature. The high temperature bending tests highlighted a transition from brittle to plastic behavior comprised between 1350 and 1400 °C and a considerable flexural strength reduction at temperatures higher than 1400 °C; moreover, the microstructural investigations carried out on the re-heated samples showed a very limited grain growth up to 1650 °C

Pre-service teachers ideas of collaborative work when using a wiki to construct a lab notebook

Due to the potential benefits of the wikis, they are increasingly gaining popularity in educational settings. In the educational context they have been used for various purposes such as managing research projects, publishing course materials and completing writing assignments. This type of Web 2.0 tool provides a number of useful functions, such as creation of content by multiple users, tracking history of users’ actions, comparison between different editions and roll-back to earlier versions of the wiki, allowing teachers to monitor learners’ co-authoring process. Because of these functions, wikis have been claimed as facilitators of collaborative writing, group discussion and interaction. However, wikis are not inherently collaborative. After a brief review of the relevant literature on the importance of interaction in the learning process this communication presents some preliminary results on the use of wikis by pre-service elementary school teachers. The implementation of virtual lab notebooks hosted within a wiki environment in the scope of a course on biology is described. Students´ perceptions regarding the implementation of the wiki are explored, namely its challenges and potential benefits. In order to achieve this goal, participants were asked to write a reflexive essay about their use of the wiki. A content analysis on this data followed. An additional goal is to understand the kind of interaction promoted by the wiki. For this purpose, the individual contributions to the wiki that occurred during the learning process were analyzed and categorized. Follow-up interviews were conducted to gain insight into students’ decisionmaking process. The results are discussed in view of identifying factors that may lead to a more successful integration of the wikis in science lessons and to improve pre-service teachers’ confidence in using Web 2.0 tools for pedagogical purposes.info:eu-repo/semantics/publishedVersio

Tribological behaviour of alumina-titania nanostructured coatings produced by air plasma spray technique

Nanostructured Al2O3-TiO2 wear resistant coatings were produced by air plasma spray from plasma-densified agglomerated nano-powders. Conventional Al2O3-TiO2 coatings were also deposited for direct comparison of tribological performance. Operating parameters were optimized by a DOE (Design of Experiment) procedure, to produce coherent and well adherent ceramic coatings and to minimize dwell times in the torch in order to reduce the risk of excessive grain growth or complete remelting. Optimal tribological behaviour was selected as the main goal function. Microstructural characterization of APS nanostructured coatings confirmed the presence of fully molten areas combined with unmolten particles still retaining their spherical morphology, and with elongated particles whose microstructure showed initial stages of grain growth and recrystallization processes. Coatings produced with the final set of deposition parameters were tested for micro-hardness, elastic modulus and unlubricated wear resistance against alumina. Results clearly indicate that nanostructured coatings produced from plasma densified nanostructured precursors exhibit considerably improved performances, evaluated in terms of worn out volume and mass loss

Enhanced lipid extraction from unbroken microalgal cells using enzymes

The marine microalga Nannochloropsis sp. was chosen as a model organism to investigate the feasibility of using cell wall-degrading enzymes to enhance the recovery of intracellular lipids. An enzyme cocktail containing galactomannanase, 1,4-β-cellobiosidase and β-glucosidase as main components was prepared from commercial enzyme preparations. The effects of pretreatment time (P), enzyme dosage (D), pH and temperature (T) on the amount of extracted lipids were investigated using response surface methodology. Under the best conditions (P = 90 min, D = 1.3 mg g–1, pH = 5, T = 36°C) over 70% of the lipids present in the microalga were recovered. SEM and TEM characterization of enzyme-treated microalgae showed extensive cell damage with significant disruption of the cell wall and release of algal material. Overall, the results of this study strongly support the use of commercial enzyme preparations to improve lipid recovery from microalgae and provide useful information on the influence of process conditions on the treatment efficiency

O uso de uma ferramenta web 2.0 para um ensino-aprendizagem colaborativo

Em educação, os wikis têm ganho uma crescente popularidade. A presente investigação pretende analisar o uso de cadernos de laboratório virtuais, realizados com recurso a um wiki, numa instituição de ensino superior em Portugal. Neste artigo, foca-se a atenção no tipo de interação que se desenvolveu entre os estudantes, em grupos de trabalho de 2 ou 3 elementos, aquando da elaboração do caderno de laboratório virtual. Com esse objetivo, analisou-se o tipo de edição e compararam-se versões sucessivas de páginas do caderno, de uma amostra de grupos que frequentaram uma unidade curricular de biologia, no âmbito da formação inicial de educadores e professores dos 1.º e 2.ºciclos. Procedeu-se à categorização de contribuições individuais para o wiki e os dados obtidos foram analisados usando uma combinação de métodos qualitativos e quantitativos. Os resultados contribuem para enriquecer a compreensão acerca do uso dos wikis em projetos educacionais de cariz colaborativo.info:eu-repo/semantics/publishedVersio

Imaging assessment and clinical significance of pneumatosis in adult patients.

Gas detection in the bowel wall and in portomesenteric venous vessels in adults has long been related to intestinal infarction and poor outcome; many case reports have shown that pneumatosis may be associated with a large variety of pathological situations, ranging from absolutely benign and asymptomatic forms to abdominal catastrophes. Several studies have been conducted on this topic with different conclusions, probably due to differences in population so that the clinical value of these signs is still questioned. Intestinal pneumatosis, especially if presenting with a band-like pattern and if associated with portomesenteric vein gas, when observed in an acute abdominal setting should raise the suspicion of mesenteric infarct and prompt a careful search for other signs of intestinal involvement, so as not to miss cases of life-threatening intestinal infarct or allow them to further evolve into extensive necrosis with worse prognosis. In this review we illustrate the most relevant aspects of these debated but significant radiological signs

Berberine reverts hepatic mitochondrial dysfunction in high-fat fed rats: A possible role for SirT3 activation

Berberine is an isoquinoline alkaloid with anti-diabetic properties. Despite the central role of liver and thus hepaticmitochondria inwhole-bodymetabolism, berberine effects on hepaticmitochondrial function in an obesity model are still unknown. Here, we demonstrate that berberine treatment recovers mitochondrial efficiency when altered by a high-fat feeding.Mitochondria isolated from the liver of high-fat fed rats exhibited decreased capacity to accumulate calcium and impaired oxidative phosphorylation (OXPHOS) capacity, as shown by impaired mitochondrialmembrane potential, oxygen consumption and cellular ATP levels. Interestingly, the recovery of mitochondrial function by berberine was associated with an increased activity of the mitochondrial sirtuin 3 (SirT3). In conclusion, berberine potent protective effects against metabolic syndrome may rely on increasing mitochondrial SirT3 activity, normalizing mitochondrial function and preventing a state of energetic deficit caused by impaired OXPHOS.JST, FVD, APG and ATV were recipients of a Fundação para a Ciência e a Tecnologia PhD scholarship (SFRH/BD/38467/2007, SFRH/BD/38372/ 2007, SFRH/BD/44674/2008 and SFRH/BD/44796/2008, respectively). This project was supported by a FCT grant PTCD/SAU-OSM/72443/ 2006

Injúria renal aguda - perspectivas contemporâneas acerca de sua fisiopatologia, diagnóstico e manejo

A Injúria Renal Aguda (IRA) representa uma condição grave caracterizada por uma rápida deterioração da função renal, resultando em lesão e comprometimento funcional. Este distúrbio é uma síndrome complexa em que o rim desempenha um papel ativo na disfunção de diversos órgãos. A incidência da IRA está em constante aumento, tornando-se uma condição prevalente e significativa em termos de impacto nos custos de saúde em nível global. Apesar de ter múltiplos mecanismos subjacentes, atualmente não há terapia farmacológica eficaz para reverter a lesão já estabelecida. A IRA, associada a uma variedade de causas, desencadeia uma resposta inflamatória que afeta órgãos distantes, aumentando substancialmente o risco de morbidade e mortalidade a longo prazo. A prevalência da condição varia devido a critérios de classificação inconsistentes e disparidades entre países com diferentes níveis de renda. Reconhecer e tratar precocemente a IRA são imperativos, ressaltando a urgência de aprimorar as práticas de detecção, diagnóstico e cuidados em todas as configurações de recursos disponíveis. A IRA é classificada em pré-renal, renal e pós-renal, sendo a lesão pré-renal a forma mais comum. Os mecanismos fisiopatológicos envolvem a ativação do sistema renina-angiotensina, hipoxemia, inflamação e estresse oxidativo. Embora muitos casos apresentem recuperação completa, a IRA pode evoluir para perda de função renal crônica. No tratamento, a ênfase recai na correção de distúrbios associados, como hipercalemia e acidose metabólica. A abordagem contemporânea envolve a identificação e tratamento das causas subjacentes, a eliminação de fatores agravantes e medidas de suporte para manter o equilíbrio hidroeletrolítico. Em situações mais severas, a terapia de substituição renal emerge como uma opção viável

Assessing impacts of soil management measures on ecosystem services

Only a few studies have quantified and measured ecosystem services (ES) specifically related to soil. To address this gap, we have developed and applied a methodology to assess changes in ecosystem services, based on measured or estimated soil property changes that were stimulated by soil management measures (e.g., mulching, terracing, no-till). We applied the ES assessment methodology in 16 case study sites across Europe representing a high diversity of soil threats and land use systems. Various prevention and remediation measures were trialled, and the changes in manageable soil and other natural capital properties were measured and quantified. An Excel tool facilitated data collection, calculation of changes in ecosystem services, and visualization of measured short-term changes and estimated long-term changes at plot level and for the wider area. With this methodology, we were able to successfully collect and compare data on the impact of land management on 15 different ecosystem services from 26 different measures. Overall, the results are positive in terms of the impacts of the trialled measures on ecosystem services, with 18 out of 26 measures having no decrease in any service at the plot level. Although methodological challenges remain, the ES assessment was shown to be a comprehensive evaluation of the impacts of the trialled measures, and also served as an input to a stakeholder valuation of ecosystem services at local and sub-national level

práticas artísticas no ensino básico e secundário

Para este número 18 da Revista Matéria-Prima reuniram-se 16 artigos que permitem colocar em perspetiva diversas dimensões da Educação Artística. Entre a consciência patrimonial e a emancipação, entre o domínio da técnica e do género, entre a integração e a maturação criadora, há um espaço a ser pesquisado, feito de história, de identidade, de ensaio e de inclusividadeinfo:eu-repo/semantics/publishedVersio