The greener grass: da autorrepresentação em Alanis Morissette

Tese de Doutoramento em Ciências da Literatura - Especialidade em Teoria da Literatura

Effect of ionic liquid anion and cation on the physico-chemical properties of poly(vinylidene fluoride)/ionic liquid blends

Poly(vinylidene fluoride), PVDF, has been blended with different ionic liquids (IL) in order to evaluate the effect of the different IL anions and cations on the electroative -phase, thermal, mechanical and electrical properties of the polymer blend. [C2MIM][Cl], [C6MIM][Cl], [C10MIM][Cl], [C2MIM][NTf2], [C6MIM][NTf2], [C10MIM][NTf2] have been selected and were introduced in the polymer at a weight percentage of 40 wt%. It was found that the incorporation of ILs into the PVDF matrix leads to an increase of the -phase content due to the strong electrostatic interactions between the dipolar moments of PVDF and the ILs. Further, the incorporation of ILs into PVDF strongly decreases the elastic modulus and increases the electrical conductivity of the blend with respect to the pure polymer matrix, all these effects being accompanied by a modification of the crystallization kinetics, as indicated by the modified spherulitic microstructure. Thus, novel PVDF/IL blends films with high transparency, excellent antistatic properties, and highly polar crystal form fraction were successfully achieved.

Gd2O3: Eu3+/PPO/POPOP/PS composites for digital imaging radiation detectors

Polymer based scintillator composites have been produced by combining polystyrene (PS) and Gd2O3:Eu3+ scintillator nanoparticles. Polystyrene has been used since it is a flexible and stable binder matrix, resistant to thermal and light deterioration and with suitable optical properties. Gd2O3:Eu3+ has been selected as scintillator material due to its wide band gap, high density and visible light yield. The optical, thermal and electrical characteristics of the composites were studied as a function of filler content, together with their performance as scintillator material. Additionally 1wt.% of 2,5 dipheniloxazol (PPO) and 0.01wt.% of (1,4-bis(2-(5-phenioxazolil))-benzol (POPOP) were introduced in the polymer matrix in order to strongly improve light yield, i.e. the measured intensity of the output visible radiation, under X-ray irradiation. Whereas increasing scintillator filler concentration (from 0.25wt.% to 7.5wt.%) increases scintillator light yield, decreases the optical transparency of the composite. The addition of PPO and POPOP, strongly increased the overall 2 transduction performance of the composite due to specific absorption and re-emission processes. It is thus shown that Gd2O3:Eu3+/PPO/POPOP/PS composites in 0.25 wt.% of scintillator content with fluorescence molecules is suitable for the development of innovate large area X-ray radiation detectors with huge demand from the industries.

Solid polymer electrolytes based on chitosan and europium triflate

Solid polymer electrolytes (SPEs) were obtained from chitosan plasticized with glycerol and contained europium (III) trifluoromethanesulfonate salt. The transparent samples were characterized by thermal analysis (DSC and TGA), impedance spectroscopy and electron paramagnetic resonance (EPR). The sample with 55.34 wt.% of europium triflate showed the best ionic conductivity of 1.52 × 10−6 and 7.66 × 10−5 S cm−1 at 30°C and 80°C, respectively. The thermal analysis revealed that the degradation started at around 130–145°C and the weight loss ranged from 20 to 40%. The DSC of the samples showed no Tg, but only a large endothermic peak that was centered between 160 and 200 °C. The EPR analysis showed a broadening of the EPR resonance lines with increasing europium contents in the chitosan membranes due to the magnetic dipole–dipole coupling and spin–spin exchange between the Eu2+ ions. Moreover, the electrolytes based on chitosan and europium triflate presented good flexibility, homogeneity, and transparency.

Silk fibroin based multifunctional materials

Silk fibroin is a commonly available natural biopolymer produced in specialized glands of arthropods, such as silkworms or spiders, scorpions, mites, bees and flies. This biopolymer has a long history of use in textile production and also as sutures or treatment of skin wounds. Silk fibroin has been increasingly explored in other areas of biomedical science where we can find a higher morphological diversification of silk biomaterials like films, electrospun fibers, 3D porous scaffolds or nanoparticles. In recent years it has been demonstrated that fibroin is an excellent material for active components in optical devices. This new application opens the way towards the development of multifunctional optoelectronic devices, which in perspective can be made fully biocompatible and eventually bioresorbable. Moreover, fibroin can be added to other biocomponents in order to modify the biomaterial properties leading to optimized and total different functions. These improvements can go from higher cell adhesion in tissue engineering or enhanced optical transparency, smoothness or flexibility in optoelectronic devices. The tuning and completely understanding of silk fibers physicochemical properties and interaction with other elements are of crucial importance for the improvement of already existent silk-based materials and the basis for the development of new products.

Lithium-doped silk fibroin films for application in electrochromic devices

Silk fibroin (SF) is a commonly available natural biopolymer produced in specialized glands of arthropods, with a long history of use in textile production and also in health cares. The exceptional intrinsic properties of these fibers, such as self-assembly, machinability, biocompatibility, biodegradation or non-toxicity, offer a wide range of exciting opportunities [1]. It has long been recognized that silk can be a rich source of inspiration for designing new materials with tailored properties, enhanced performance and high added value for targeted applications, opening exciting new prospects in the domain of materials science and related technological fields, including bio-friendly integration, miniaturization and multifunctionalization. In recent years it has been demonstrated that fibroin is an excellent material for active components in optics and photonics devices. Progress in new technological fields such as optics, photonics and electronics are emerging [2,3]. The incorporation of polymer electrolytes as components of various devices (advanced batteries, smart windows, displays and supercapacitors) offers significant advantages with respect to traditional electrolytes, including enhanced reliability and improved safety. SF films are particularly attractive in this context. They have near-perfect transparency across the VIS range, surface flatness (together with outstanding mechanical robustness), ability to replicate patterned substrates and their thickness may be easily tailored from a few nanometers to hundreds of micrometers through spin-casting of a silk solution into subtract. Moreover, fibroin can be added to other biocomponents or salts in order to modify the biomaterial properties leading to optimized and total different functions. Preliminary tests performed with a prototype electrochromic device (ECD) incorporating SF films doped with lithium triflate and lithium tetrafluoroborate (LiTFSI and LiBF4, respectively) as electrolyte and WO3 as cathodic electrochromic layer, are extremely encouraging. Aiming to evaluate the performance of the ion conducting SF membranes doped with LiTFSI and LiBF4 (SF-Li), small ECDs with glass/ITO/WO3/SF-Li/CeO2-TiO2/ITO/glass configuration were assembled and characterized. The device exhibited, after 4500 cycles, the insertion of charge at -3.0 V reached –1.1 mC.cm-2 in 15 s. After 4500 cycles the window glass-staining, glass/ITO/WO3/Fibrin-Li salts electrolyte/CeO2-TiO2/ITO/glass configuration was reversible and featured a T  8 % at λ = 686 nm

O processo de adoção e implementação do Orçamento Participativo: os casos de Braga e Guimarães

Dissertação de mestrado em Administração Pública (área de especialização em Gestão Pública)

Enquadramento para a compreensão dos impactos do Open Government Data

Dissertação de mestrado integrado em Engenharia e Gestão de Sistemas de Informação

Divulgação de informação sobre o governo das sociedades em Portugal: Extensão e determinantes

Tese de Doutoramento em Contabilidade

Formação e avaliação de desempenho: contributos para o desenvolvimento profissional

Tese de Doutoramento em Ciências da Educação (Especialidade em Desenvolvimento Curricular)

Production of elastic Chitosan/Chondroitin sulphate multilayer films for tissue regeneration

Membrane-like scaffolds are suitable to induce regeneration in many and different anatomic sites, such as periodontal membrane, skin, liver and cardiac tissues. In some circumstances, the films should adapt to geometrical changes of the attached tissues, such as in cardiac or blood vessel tissue engineering applications. In this context, we developed stretchable two-dimensional multilayer constructs through the assembling of two natural-based polyelectrolytes, chitosan (CHT) and chondroitin sulphate (CS), using the layer-by-layer methodology. The morphology, topography and the transparency of the films were evaluated. The in- fluence of genipin, a natural-derived cross-linker agent, was also investigated in the control of the mechanical properties of the CHT/CS films. The water uptake ability can be tailored by changing the cross-linker concentration, which influenced the young modulus and ultimate tensile strength. The maximum extension tends to decrease with the increase of genipin concentration, compromising the elastic properties of CHT/CS films: nevertheless using lower cross-linker contents, the ultimate tensile stress is similar to the films not cross-linked but exhibiting a significant higher modulus. The in vitro biological assays showed better L929 cell adhesion and proliferation when using the crosslinked membranes and confirmed the non-cytotoxicity of the CHT/CS films. The developed free-standing biomimetic multilayer could be designed to fulfill specific therapeutic requirements by tuning properties such as swelling, mechanical and biological performances.

Redes sociais como ferramenta para a divulgação de ações de responsabilidade social corporativa: o estudo de caso da TOMS

Relatório de estágio de mestrado em Ciências da Comunicação (área de especialização em Publicidade e Relações Públicas)

Plano de revitalização do centro histórico de Braga

Dissertação de mestrado em Políticas Comunitárias e Cooperação Territorial

Investigating a galactomannan gel obtained from Cassia grandis seeds as immobilizing matrix for Cramoll lectin

Characterization, with emphasis on the rheological properties, of Cassia grandis seeds galactomannan gel containing immobilized Cramoll 1,4 is presented. The gels, with and without immobilized Cramoll 1,4, were evaluated along time by rheometry, pH, color, microbial contamination and lectin hemagglutinating activity (HA). Rheological determinations confirmed the gels to be very stable up to 30 days with variations occurring after this period. Rheological data also showed that the gel/Cramoll 1,4 immobilizing matrix loses its elastic modulus substantially after 60 days. Both gels presented no microbial contamination as well as a pH close to neutral. Colorimetric parameters demonstrated the gels transparency with occasional yellowness. The opacity of the galactomannan gel did not change significantly along the study; the same did not occur for the gel with immobilized Cramoll 1,4 as a statistically significant reduction of its opacity was observed. In what concerns immobilized Cramoll 1,4HA, up to 90% of its initial HA was maintained after 20 days, with a decrease to 60% after 60 days. These results combined with the thickening and stabilizing characteristics of the galactomannan gel make this gel a promising immobilizing matrix for Cramoll 1,4 that can be further exploited for clinical and cosmetic applications.

Production and extraction of polysaccharides and oligosaccharides and their use as new food additives

Polysaccharides and oligosaccharides can improve quality and enhance nutritional value of final food products due to their technological and nutritional features ranging from their capacity to improve texture to their effect as dietary fibers. For this reason, they are among the most studied ingredients in the food industry. The use of natural polysaccharides and oligosaccharides as food additives has been a reality since the food industry understood their potential technological and nutritional applications. Currently, the replacement of traditional ingredients and/or the synergy between traditional ingredients and polysaccharides and oligosaccharides are perceived as promising approaches by the food industry. Traditionally, polysaccharides have been used as thickening, emulsifying, and stabilizing agents, however, at this moment polysaccharides and oligosaccharides claim health and nutritional advantages, thus opening a new market of nutritional and functional foods. Indeed, their use as nutritional food ingredients enabled the food industry to develop a countless number of applications, e.g., fat replacers, prebiotics, dietary fiber, and antiulcer agents. Based on this, among the scientific community and food industry, in the last years many research studies and commercial products showed the possibility of using either new or already used sources (though with changed properties) of polysaccharides for the production of food additives with new and enhanced properties. The increasing interest in such products is clearly illustrated by the market figures and consumption trends. As an example, the sole market of hydrocolloids is estimated to reach $7 billion in 2018. Moreover, oligosaccharides can be found in more than 500 food products resulting in a significant daily consumption. A recent study from the Transparency Market Research on Prebiotic Ingredients Market reported that prebiotics' demand was worth $2.3 billion in 2012 and it is estimated to reach $4.5 billion in 2018, growing at a compound annual growth rate of 11.4% between 2012 and 2018. The entrance of this new generation of food additives in the market, often claiming health and nutritional benefits, imposes an impartial analysis by the legal authorities regarding the accomplishment of requirements that have been established for introducing novel ingredients/food, including new poly- and oligosaccharides. This chapter deals with the potential use of polysaccharides and oligosaccharides as food additives, as well as alternative sources of these compounds and their possible applications in food products. Moreover, the regulation process to introduce novel polysaccharides and oligosaccharides in the market as food additives and to assign them health claims is discussed.