A new chemical route to synthesise TM-doped (TM = Co, Fe) TiO2 nanoparticles

Since the discovery of ferromagnetism well above room temperature in the Co-doped TiO2 system, diluted magnetic semiconductors based on TiO2 doped with transition metals have generated great interest because of their potential use in the development of spintronic devices. The purpose of this paper is to report on a new and swift chemical route to synthesise highly stable anatase single-phase Co- and Fe-doped TiO2 nanoparticles, with dopant concentrations of up to 10 at.-% and grain sizes that range between 20 and 30 nm. Complementary structural, microstructural and chemical analyses of the different nanopowders synthesised strongly support the hypothesis that a homogeneous distribution of the dopant element in the substitutional sites of the anatase structure has been achieved. Moreover, UV/Vis diffuse reflectance spectra of powder samples show redshifts to lower energies and decreasing bandgap energies with increasing Co or Fe concentration, which is consistent with n-type doping of the TiO2 anatase matrix. Films of Co-doped TiO2 were successfully deposited onto Si (100) substrates by the dip-coating method, with suspensions of Ti1-xCOxO2 nanoparticles in ethylene glycol. ((C)Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

Avaliação da qualidade química e microbiológica de tintas didácticas do ensino pré-escolar

As tintas utilizadas nas actividades didácticas possuem na sua composição ingredientes que dada a sua natureza, modo de fabrico e de utilização, podem representar um risco para a saúde das crianças. Neste âmbito, procurou-se com este estudo avaliar a qualidade química e microbiológica das tintas utilizadas pelas crianças no ensino pré-escolar. Vinte e nove amostras de tintas, incluindo guaches, tintas de águas, digitintas e tintas para pinturas faciais foram recolhidas em oito estabelecimentos de ensino, nomeadamente, Jardins de Infância, do conselho de Vila Nova de Gaia. A avaliação microbiológica envolveu não só a determinação da concentração microbiana presente nas amostras, como também, a avaliação da estabilidade microbiana nas tintas das espécies S.aureus e E.coli. Na avaliação química procedeu-se à determinação da concentração dos metais chumbo (Pb), cádmio (Cd), crómio (Cr), cobalto (Co), níquel (Nq), manganês (Mn), cobre (Cu) e zinco (Zn) quer em algumas das amostras recolhidas nos estabelecimentos de ensino, quer em tintas adquiridas em três estabelecimentos comerciais. Os resultados obtidos da avaliação microbiológica revelam uma contaminação estática na generalidade das tintas. Três amostras de tintas apresentaram ainda elevada contaminação por fungos, nomeadamente Aspergillus spp. e Trichophyton spp. Da avaliação da estabilidade microbiana das espécies S.aureus e E.coli observou-se uma sensibilidade das mesmas às tintas, sendo evidenciado, em alguns casos, um decrescimento da concentração ao longo do tempo de exposição, e noutros, uma sensibilidade imediata. A espécie S.aureus revelou, contudo, maior capacidade de resistência que a E.coli. Os resultados obtidos da avaliação química revelaram a presença de Cr em todas as amostras, registando as tintas adquiridas em estabelecimentos comerciais concentrações mais elevadas para este metal. Os metais Cu e Zn foram detectados, em algumas amostras de tintas artísticas, em concentrações acima dos valores limites. Nas tintas para a cara foram encontrados os metais Pb, Cd, Cr e Nq, cuja utilização é interdita nestes produtos. O conhecimento das características químicas e microbiológicas das tintas utilizadas por crianças do ensino pré-escolar revelou-se de grande importância, nomeadamente, para a determinação dos riscos a que este grupo de indivíduos pode estar exposto no seu dia-a-dia quando utilizam estes produtos.

Effect of Chemical Pretreatments on the Physical Properties of Kiwi

In this work the effect of pre-treatments on the physical properties of fresh kiwi was studied. For that, a set of tests using chemical pretreatments was used, in which the samples were subjected to aqueous solutions of ascorbic acid and potassium metabisulfite at concentrations of 0.25% and 1% (w/v) for periods of 30 and 60 minutes, in order to understand the implications of the treatments in the color and texture of the kiwi as compared to its original properties. The results showed that the kiwi treated with ascorbic acid changed its color very intensively when compared to the fresh product, and this trend was intensified after storage. Contrarily, when potassium metabisulfite was used, the changes in color were quite negligible right after the treatment and even lower after the storage period of 6 days under refrigeration. After the treatments with both solutions, the kiwi texture was drastically changed, diminishing hardness considerably and increasing elasticity for all treatments. The same could be observed after six days of refrigeration.

ß-Lactams: chemical structure, mode of action and mechanisms of resistance

This synopsis summarizes the key chemical and bacteriological characteristics of β-lactams, penicillins, cephalosporins, carbanpenems, monobactams and others. Particular notice is given to first-generation to fifth-generation cephalosporins. This review also summarizes the main resistance mechanism to antibiotics, focusing particular attention to those conferring resistance to broad-spectrum cephalosporins by means of production of emerging cephalosporinases (extended-spectrum β-lactamases and AmpC β-lactamases), target alteration (penicillin-binding proteins from methicillin-resistant Staphylococcus aureus) and membrane transporters that pump β-lactams out of the bacterial cell.

Historical Heritage: A Study to Conservation

Considering ancient monuments and historical buildings, it seems that these mortars have proved to be durable and reliable materials. The restoration and maintenance of old renders is one of the key aspects of correct rehabilitation practice. The ideal course of action is to replace the damaged material by a material with compatible characteristics.The study in development presents the chemical, physical and morphologic analysis performed for ancient air lime mortars belonging to historical monuments: Santa Marta Fortress in the coast line Lisbon-Cascais dated from XVII century and Defense Wall of Lisbon dated from XI century, which layout could be associated to roman period. It is important to underline that the studied samples of ancient portuguese air lime mortars, have been submitted during centuries to very severe maritime environment that includes daily cycles of wet/dry, wind, friction and the constant presence of salts, generally aggressive. However, they show very good performance and conservation state, unlike most of the new air lime mortars, which are generally considered weak, not very durable, materials. This work is included in a study intending to determine key factors to the durability of these ancient materials in presence of water. Visible reaction rims around some aggregates suggests the occurrence of pozzolanic reactions between aggregates and the lime binder that creates neoformation products, such as calcium-silico-aluminates, which seems be, besides the pores filling, the responsible for the resistance and cohesion of these ancient mortars submitted to aggressive humid environments.

Comparison of Py-GC/FID and Wet Chemistry Analysis for Lignin Determination in Wood and Pulps from Eucalyptus globulus

The kraft pulps produced from heartwood and sapwood of Eucalyptus globulus at 130 degrees C, 150 degrees C, and 170 degrees C were characterized by wet chemistry (total lignin as sum of Klason and soluble lignin fractions) and pyrolysis (total lignin denoted as py-lignin). The total lignin content obtained with both methods was similar. In the course of delignification, the py-lignin values were higher (by 2 to 5%) compared to Klason values, which is in line with the importance of soluble lignin for total lignin determination. Pyrolysis analysis presents advantages over wet chemical procedures, and it can be applied to wood and pulps to determine lignin contents at different stages of the delignification process. The py-lignin values were used for kinetic modelling of delignification, with very high predictive value and results similar to those of modelling using wet chemical determinations.

Physical-chemical and mineralogical characterization of fine aggregates from construction and demolition waste recycling plants

Construction and demolition waste (CDW) represents around 31% of all waste produced in the European Union. It is today acknowledged that the consumption of raw materials in the construction industry is a non-sustainable activity. It is thus necessary to reduce this consumption, and the volume of CDW dumped, by using this waste as a source of raw materials for the production of recycled aggregates. One potential use of these aggregates is their incorporation in reinforced concrete as a replacement of natural aggregates. A concrete that incorporates these aggregates and still performs well requires them to be fully characterized so that their behaviour within the concrete can be predicted. Coarse recycled aggregates have been studied quite thoroughly, because they are simpler to reintroduce in the market as a by-product, and so has the performance of concrete made with them. This paper describes the main results of research designed to characterize the physical and chemical properties of fine recycled aggregates for concrete production and their relationship with mineralogical composition and preprocessing. The constraints of the incorporation of fine aggregates in reinforced concrete are discussed. It is shown that, unless a developed processing diagram is used, this application is not feasible. (C) 2013 Elsevier Ltd. All rights reserved.

The surplus value of Azorean macroalgae as health-promoting food. Protein, fiber, carbohydrates, lipids and vitamins determination

AICMA 2012 (BIT's 1st Annual International Congress of Marine Algae), World Expo Center, Dalian, China, 20-23 de Setembro.

Size-segregated chemical composition of aerosol emissions in an urban road tunnel in Portugal

An atmospheric aerosol study was performed in 2008 inside an urban road tunnel, in Lisbon, Portugal. Using a high volume impactor, the aerosol was collected into four size fractions (PM0.5, PM0.5-1, PM1-2.5 and PM2.5-10) and analysed for particle mass (PM), organic and elemental carbon (OC and EC), polycyclic aromatic hydrocarbons (PAH), soluble inorganic ions and elemental composition. Three main groups of compounds were discriminated in the tunnel aerosol: carbonaceous, soil component and vehicle mechanical wear. Measurements indicate that Cu can be a good tracer for wear emissions of road traffic. Cu levels correlate strongly with Fe, Mn, Sn and Cr, showing a highly linear constant ratio in all size ranges, suggesting a unique origin through sizes. Ratios of Cu with other elements can be used to source apportion the trace elements present in urban atmospheres, mainly on what concerns coarse aerosol particles. (C) 2013 Elsevier Ltd. All rights reserved.

Estudo de esmalte estufa aquoso definitivo

Mestrado em Engenharia Química

Iron oxide/gold core/shell nanomagnetic probes and CdS biolabels for amplified electrochemical immunosensing of Salmonella typhimurium

There is an imminent need for rapid methods to detect and determine pathogenic bacteria in food products as alternatives to the laborious and time-consuming culture procedures. In this work, an electrochemical immunoassay using iron/gold core/shell nanoparticles (Fe@Au) conjugated with anti-Salmonella antibodies was developed. The chemical synthesis and functionalization of magnetic and gold-coated magnetic nanoparticles is reported. Fe@Au nanoparticles were functionalized with different self-assembled monolayers and characterized using ultraviolet-visible spectrometry, transmission electron microscopy, and voltammetric techniques. The determination of Salmonella typhimurium, on screen-printed carbon electrodes, was performed by square-wave anodic stripping voltammetry through the use of CdS nanocrystals. The calibration curve was established between 1×101 and 1×106 cells/mL and the limit of detection was 13 cells/mL. The developed method showed that it is possible to determine the bacteria in milk at low concentrations and is suitable for the rapid (less than 1 h) and sensitive detection of S. typhimurium in real samples. Therefore, the developed methodology could contribute to the improvement of the quality control of food samples.

Selecção do melhor descolorante para a eliminação da cor residual num efluente têxtil

Mestrado em Engenharia Química

Influence of the pre-treatments on the properties of biodegradable films from bovine hair

The replacement of conventional synthetic films and coatings by biodegradable alternatives reduces the use of non-renewable resources and waste disposal problems. Considering that Portugal is a major producer of leather, and consequently a large producer of related wastes, in this research, bovine hair was tested for the production of biodegradable films directly by thermo-compression, allowing waste valorisation and reduction of environmental pollution. The aim of this study was to determine the influence of the different pre-treatments performed by two processes (removal by mechanical action and removal by chemical process), applied to bovine hair, in order to obtain a biodegradable film with appropriate properties. Mechanical properties for these films were evaluated, namely strain at break, stress at break and Young modulus. Additionally colour, solubility and swelling in water were also studied. The mechanical removal hair only produced films with Na2S treatment. Chemical removed hair (immunization) depends of the pre-treatment and the degreasing with petroleum ether or sodium sulphide pre-treatment leads better mechanical properties. The results obtained indicated that the pre-treatments have an important role in the final properties of biodegradable films.

Contribuição para a valorização de produtos lácteos dos Açores : qualificação e caracterização da manteiga açoriana

Dissertação de Mestrado em Tecnologia e Segurança Alimentar

Desenvolvimento de tecnologias de extração e de quantificação dos principais componentes nutricionais de macroalgas do litoral dos Açores tendo em vista o seu aproveitamento como suplemento alimentar

Dissertação de Mestrado em Tecnologia e Segurança Alimentar