Conformação automática de formas complexas em vidro de mesa

Os objectivos do presente trabalho foram a investigação dos principais defeitos que ocorrem nos produtos de vidro de mesa produzidos por processos automáticos e o desenvolvimento de novos vidros e tecnologias que permitam aumentar os rendimentos de produção, ou a flexibilidade da operação de conformação. A viscosidade influencia a facilidade de conformação dos produtos. Temperaturas de gota mais baixas, espessuras de parede de produtos mais elevadas e baixas áreas de transferência térmica facilitam a ocorrência de defeitos, sobretudo mecânicos e de superfície. Foram identificados os produtos de vidro de mesa que apresentam maiores dificuldades na conformação, designados por produtos de forma complexa. Por ser um factor relevante na prática, discutiu-se o efeito da quantidade de casco usado na elaboração dos vidros sobre a conformação de produtos de forma complexa. A quantidade de casco influencia a volatilização de fundentes que por sua vez tem efeito sobre as propriedades de trabalhabilidade do vidro. Desenvolveram-se novos vidros compatíveis com a utilização de queimos enriquecidos em oxigénio que são utilizados para reduzirem os defeitos mecânicos e de superfície nos produtos de vidros de mesa prensados. A compatibilidade vidro/tecnologia fez-se com uma modificação do sistema de afinação do vidro. Os vidros modificados apresentam propriedades físicoquímicas semelhantes à do vidro inicial e por isso indicam viabilidade comercial. A tecnologia dos canais corantes foi utilizada para modificar a trabalhabilidade de um vidro base a partir da introdução até 5 % de fritas incolores ricas em Li2O. Os valores de RMS (velocidade relativa de máquina) desceram de 106,8 % para 95,7 % enquanto os valores de Pt (patamar de trabalho) subiram de 100,6 s para 111,3 s com o aumento de frita. As propriedades físico-químicas dos vidros aditivados com frita indicam viabilidade comercial. Esta inovação tecnológica introduz flexibilidade nos processos industriais vidreiros. A composição química do vidro e por isso as propriedades relacionadas com a trabalhabilidade podem ser entendidas como mais uma variável dos processos de conformação e usadas em função das técnicas de conformação disponíveis, da forma dos objectos a conformar e da engenharia da ferramenta moldante utilizada. Foi observada convergência entre os resultados experimentais e os valores calculados a partir dos modelos de Huff e Fluegel nos principais parâmetros da tecnologia vidreira (RMS e Pt) e nas propriedades dos vidros nomeadamente densidade e coeficiente de dilatação térmico. Uma parte importante deste trabalho decorreu em ambiente industrial. Em temas relacionados com a investigação do processamento vidreiro industrial, a prática de desenvolver trabalho experimental integrado no próprio ambiente industrial está claramente documentada na bibliografia publicada em revistas e jornais de referência internacional. ABSTRACT: The research on the causes of major defects that occur in glass tableware products produced by automatic processes and the development of new glasses and technologies for increasing the production efficiency, or the flexibility of operation were the objectives of the Thesis project. Viscosity influences the flexibility of glass forming. Lower drop temperatures, high product wall thicknesses, or low areas of heat transfer facilitate the occurrence of defects, mainly mechanical and surface born. We identified the products of glass tableware showing the greatest difficulties in forming, designated as complex shape products. The effect of the amount of recycled glass used in the preparation of glass batches on the conformation of products of complex shapes and on glass workability is discussed. The amount of recycled glass affects the volatilization of glass modifiers which in turn have an effect on the glass properties and workability. New glasses which become compatible with the use of oxygen burners were formulated, tested and developed to the industrial use, oxygen enrichment being used to reduce the mechanical and surface defects in pressed glass tableware. Compatibility glass / technology was achieved with a modified system of tuning of the glass. The modified glasses have physical and chemical properties similar to the original glass and therefore are commercially viable. The technology of the colouring channels was used to change glass workability of a glass base by the introduction of up to 5 % Li2O rich in colourless frit. The values of RMS (relative machine speed) fell from 106.8 % to 95.7 % while the values of Pt (cooling time) increased from 100.6 s to 111.3 s by the introduction of glass frits. The physico-chemical properties of the modified glass show commercial viability. This technology introduces flexibility in industrial processes of glass. The chemical composition of glass and therefore the properties related to workability can be understood as another variable of the glass forming processes and used according to the available forming techniques, the shape of objects and the engineering tools used for the moulds. Convergence was observed between experimental and predicted from Huff and Fluegel models in studying the properties of glasses. An important part of this work was done inside the industrial environment. On issues related to the investigation of the glass processing inside the industry, the practice of developing experimental work integrated in the industrial environment is clearly documented and referenced in the published literature in international journals and periodicals.

Soil erosion mitigation following forest wildfires

This study aims to measure the effectiveness of four post-fire emergency techniques for reducing overland flow and soil erosion on the central-Portugal typical forest. The selection and development of these techniques was based on the review of the scientific background, but specially after checking throughout field rainfall simulation experiments which factors were the key for runoff and soil erosion on the specific case of high repellent soils. The forest residue mulch, a new treatment never tested before, was highly effective in reducing runoff and soil erosion in recently burnt eucalypt forest. The logging slash mulch had no obvious effect, but it was attributed to the small amounts of runoff and sediments that the untreated plots produced due to the extensive needle cast following a low severity fire. The hydromulch, a mixture of water, organic fibres, seeds, nutrients and a surfactant used in cutted slopes rehabilitation was also highly successful and was specially indicated for especially sensible areas. The utilization of polyacrylamides, a chemical agent with good performance in agricultural erosion, was not successful in post-fire runoff and soil erosion control, once that did not alter the most important key factor for soil erosion: the ground cover. The development of a new fibre optic turbidity sensor was a successful development on the soil erosion determination methodology, and its patent is being processed in the mean time.

Mitochondrial plasticity in pathophysiological conditions

Both skeletal and cardiac muscles daily burn tremendous amounts of ATP to meet the energy requirements for contraction. So, it is not surprising that the maintenance of mitochondrial morphology, number, distribution and functionality in striated muscle are important for muscle homeostasis. In these tissues mitochondria present the added dimension of two populations, the intermyofibrillar (IMF) and the subsarcolemmal (SS) mitochondria, being IMF the most abundant one. In the present thesis, the molecular mechanisms harboured in mitochondria of striated muscles were studied using animal models, to better comprehend the role of mitochondrial plasticity in several pathophysiological conditions such as aging, diabetes mellitus and bladder cancer. The comparative analysis of IMF and SS populations isolated from heart evidenced a higher respiratory chain activity of mitochondria interspersed in the contractile apparatus. The higher susceptible of SS respiratory chain complexes subunits to carbonylation, but not to nitration, seems to justify the lower respiratory chain activity observed in this mitochondrial population. Our results showed that in heart from aged mice there is an accumulation of dysfunctional mitochondria. The age-related decrease of oxidative phosphorylation activity seems to be justified, at least partially, by the increased proneness of mitochondrial proteins as OXPHOS subunits and MnSOD to oxidative modifications. Moreover, a sedentary lifestyle seems to worsen the functional consequences of aging in heart by increasing mitochondrial proteins susceptibility to nitration. In skeletal muscle from rats with type 1 diabetes mellitus induced by streptozotocin administration, we verified the accumulation of dysfunctional mitochondria due, at least in part, to the impairment of PQC system. Indeed, the decreased activity of AAA proteases was accompanied by the accumulation of oxidatively modified mitochondrial proteins with impact in respiratory chain activity. The diminishing of mitochondria activity also underlies cancer-induced muscle wasting. Indeed, using a rat model of chemically induced urothelial carcinoma we verified that the loss of gastrocnemius mass was related to mitochondrial dysfunction due to, at least partially, the down-regulation of PQC system involving the mitochondrial proteases paraplegin and Lon. PQC impairment resulted in the accumulation of oxidatively modified mitochondrial proteins. In overall, regardless the pathophysiological stimuli that promote mitochondrial alterations, there are similarities in the pattern of disease-related mitochondrial plasticity. The diminished capacity for ATP production in striated muscle seems to be due to increased oxidative damage of mitochondrial proteins, namely subunits of respiratory chain complexes, metabolic proteins and MnSOD. Our data highlighted, for the first time, the impact of mitochondrial PQC system impairment in the accumulation of oxidized proteins, exacerbating the dysfunction of this organelle in striated muscle in several pathophysiological conditions.

Understanding and modelling hydrological and soil erosion processes in burnt forest catchments

Forest fires implications in overland flow and soil erosion have been researched for several years. Therefore, is widely known that fires enhance hydrological and geomorphological activity worldwide as also in Mediterranean areas. Soil burn severity has been widely used to describe the impacts of fire on soils, and has being recognized as a decisive factor controlling post-fire erosion rates. However, there is no unique definition of the term and the relationship between soil burn severity and post-fire hydrological and erosion response has not yet been fully established. Few studies have assessed post-fire erosion over multiple years, and the authors are aware of none which assess runoff. Small amount of studies concerning pre-fire management practices were also found. In the case of soil erosion models, the Revised Universal Soil Loss Equation (RUSLE) and the revised Morgan–Morgan–Finney (MMF) are well-known models, but not much information is available as regards their suitability in predicting post-fire soil erosion in forest soils. The lack of information is even more pronounced as regards post-fire rehabilitation treatments. The aim of the thesis was to perform an extensive research under the post fire hydrologic and erosive response subject. By understanding the effect of burn severity in ecosystems and its implications regarding post fire hydrological and erosive responses worldwide. Test the effect of different pre-fire land management practices (unplowed, downslope plowed and contour plowed) and time-since-fire, in the post fire hydrological and erosive response, between the two most common land uses in Portugal (pine and eucalypt). Assess the performance of two widely-known erosion models (RUSLE and Revised MMF), to predict soil erosion rates during first year following two wildfires of distinctive burn severity. Furthermore, to apply these two models considering different post-fire rehabilitation treatments in an area severely affected by fire. Improve model estimations of post-fire runoff and erosion rates in two different land uses (pine and eucalypt) using the revised MMF. To assess these improvements by comparing estimations and measurements of runoff and erosion, in two recently burned sites, as also with their post fire rehabilitation treatments. Model modifications involved: (1) focusing on intra-annual changes in parameters to incorporate seasonal differences in runoff and erosion; and (2) inclusion of soil water repellency in runoff predictions. Additionally, validate these improvements with the application of the model to other pine and eucalypt sites in Central Portugal. The review and meta-analysis showed that fire occurrence had a significant effect on the hydrological and erosive response. However, this effect was only significantly higher with increasing soil burn severity for inter-rill erosion, and not for runoff. This study furthermore highlighted the incoherencies between existing burn severity classifications, and proposed an unambiguous classification. In the case of the erosion plots with natural rainfall, land use factor affected annual runoff while land management affected both annual runoff and erosion amounts significantly. Time-since-fire had an important effect in erosion amounts among unplowed sites, while for eucalypt sites time affected both annual runoff and erosion amounts. At all studied sites runoff coefficients increase over the four years of monitoring. In the other hand, sediment concentration in the runoff, recorded a decrease during the same period. Reasons for divergence from the classic post-fire recovery model were also explored. Short fire recurrence intervals and forest management practices are viewed as the main reasons for the observed severe and continuing soil degradation. The revised MMF model presented reasonable accuracy in the predictions while the RUSLE clearly overestimated the observed erosion rates. After improvements: the revised model was able to predict first-year post-fire plot-scale runoff and erosion rates for both forest types, these predictions were improved both by the seasonal changes in the model parameters; and by considering the effect of soil water repellency on the runoff, individual seasonal predictions were considered accurate, and the inclusion of the soil water repellency in the model also improved the model at this base. The revised MMF model proved capable of providing a simple set of criteria for management decisions about runoff and erosion mitigation measures in burned areas. The erosion predictions at the validation sites attested both to the robustness of the model and of the calibration parameters, suggesting a potential wider application.