Uncertainty estimation to evaluate mass balances on a combustion system

Mass balances of ash and potassium for a fluidized bed combustor were performed incorporating measurement uncertainties. The total output mass of ash or a chemical element should be equal to the mass in the input fuel; however, this is not often achieved. A realistic estimation of recovery uncertainty can support the reliability of a mass balance. Estimation of uncertainty helps to establish a reliable evaluation of the recovery ratio of ash mass and elemental mass. This may clarify whether any apparent lack in closing the mass balance can be attributed to uncertainties. The evaluation of measurement uncertainty for different matrices, namely coal, biomass, sand and ashes from different streams was based on internal quality control data and external quality control data, namely analysis of samples from proficiency tests or use of a certified reference material. The evaluation of intermediate precision and trueness allowed the estimation of measurement uncertainty. Due to the different physic and chemical characteristics of the studied matrices, the uncertainty of precision was evaluated using R-charts of data obtained from the analysis of duplicates for the majority of samples. This allowed evaluating sample heterogeneity effects. The instrumental acceptance criterion was also considered and included in the combined uncertainty. The trueness was evaluated using data from several proficiency tests and from analysis of a certified reference material or sample spiking. Statistically significant bias was included

Use of chemical fractionation to understand partitioning of biomass ash constituents during co-firing in fluidized bed combustion

Three species of biomass origin (straw pellets, olive cake and wood pellets) and two coals from different countries (Coal Polish and Coal Colombian) have been studied to understand the fate of their ash forming matter during the combustion process and to investigate the influence of co-firing biomass with coal. Three different approaches to investigate the ash behaviour were employed: (1) chemical fractionation analysis to evaluate the association/reactivity of ash forming elements in the fuels as a prediction tool, (2) establishment of elements partitioning in ash streams produced in the combustion and co-combustion trials, and (3) evaluation of enrichment factors of elements in the ash streams. The chemical fractionation analysis was applied to all fuels used to evaluate how the association/reactivity of elements making up ash may influence their behaviour during combustion. Combustion tests were carried out on a pilot scale fluidized bed combustor (FBC). Four ash streams were obtained at different locations. The uncertainty of measurements was estimated allowing a critical evaluation of mass balances over the combustion system and the partitioning of elements in the ash streams. The enrichment factors of elements in the several ash streams were estimated, incorporating uncertainties associated with analytical measurements. Results obtained showed that for FBC the relation between the chemical fractionation and the experimental partitioning is strongly affected by elutriation of particles. The element enrichment factor estimated for each ash stream, using Al as a reference element, revealed better correlations with the elements reactivity obtained by chemical fractionation because it overcomes particles elutriation effects. Nevertheless, it was observed that the reactivity estimated by chemical fractionation could not be solely interpreted as tendency of the elements to volatilize on FBC system, as reaction in bed zone of boiler may also occur retaining reactive elements

Análise dos significados construídos pelos estudantes sobre a simulaçãocomputacional do interferômetro de Mach-Zehnder no ensino médio tecnológico

Neste trabalho investigamos os significados construídos sobre o laboratório de simulação computacional, utilizando a simulação do interferômetro de Mach-Zehnder (IMZ), por estudantes da educação básica tecnológica de três turmas do ensino médio técnico integrado do Instituto Federal de Educação, Ciência e Tecnologia da Bahia nos Campus de Salvador e Camaçari. Realizamos filmagens durante as aulas sobre a dualidade da luz no ensino médio como forma de introduzir os conceitos de física quântica e através da metodologia de análise discursiva textual interpretamos os significados construídos pelos estudantes. Por fim, apresentamos os significados construídos na atividade e apontamos potencialidades e limitações desta quando realizada isoladamente sem o laboratório convencional

Drawbacks of ovarian ablation with goserelin in women with breast cancer

In the last few years, ovarian ablation with GnRH agonists has been used as first-line adjuvant therapy in pre and perimenopausal breast cancer. These drugs suppress ovarian function in the hypothalamic-pituitary axis and they have adverse effects in other end-organs. A retrospective study was conducted on 35 premenopausal women, with breast cancer, and treated with goserelin, in order to investigate the effects of iatrogenic estrogen suppression. All women complaint of amenorrhea and only half of them referred hot-flashes, weight gain or arthralgias. Hot-flushes and arthralgias remit spontaneously in the end of the treatment. Osteodensitometry was used to access bone mass. There was a reduction in mineral bone mass and T-score at femoral neck and lumbar spine after the treatment with goserelin, but without statistical significance, except for the T-score in lumbar spine

Evaluation of slagging and fouling tendency during biomass co-firing with coal in a fluidized bed

Over the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physicalechemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K2SO4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets

Adenocarcinoma do pâncreas localmente avançado e metastizado com resposta completa a quimioterapia

Os autores apresentam o caso clínico de doente do sexo feminino, 54 anos, raça branca, que recorreu ao médico assistente por dor abdominal associada a manifestações constitucionais. A ecografia revelou massa pancreática e formações nodulares hepáticas compatíveis com lesões secundárias, resultado posteriormente corroborado por tomografia computorizada, que acrescentou critérios de irressecabilidade, nomeadamente invasão dos vasos mesen- téricos e do duodeno. A biopsia ecoguiada obteve material cujo estudo anatomopatológico revelou tratar-se de adeno- carcinoma do pâncreas. Iniciou quimioterapia, verifican- do-se melhoria clínica progressiva. A reavaliação imagio- lógica, após 7 ciclos de tratamento, não detectou a lesão primitiva nem as lesões secundárias, sugerindo resposta completa. Foi mantido esquema regular de quimioterapia, persistindo a remissão 8 meses após a documentação da resposta completa