Time filter

Source Type

Porto, Portugal

Cunha S.C.,University of Porto | Kalachova K.,Institute of Chemical Technology Prague | Pulkrabova J.,Institute of Chemical Technology Prague | Fernandes J.O.,University of Porto | And 3 more authors.
Chemosphere | Year: 2010

Dust is the repository of various compounds including flame retardants. In this study an analytical method based on PLE extraction and gas chromatography-mass spectrometry was selected for the analysis of 16 PBDEs congeners in house and car dust samples collected in Portugal. The analytical performance of the method was validated using standard reference material (SRM); values from 90% to 109% and from 2% to 11% were obtained for recovery and precision, respectively. The PBDE congeners distribution in whole and sieved fractions of the dust samples, as well as influence of the source on the levels of these contaminants, were obtained. The wide range of PBDEs contents found in the dust samples indicates heterogeneous levels of contamination in these matrices. The clearest feature of the results obtained was that Deca-BDE was the main PBDE in both house and car dust samples. The total PBDEs measured in house dust (ranging from 34 to 1928 ng g-1) was lower than those found in car dust (ranging from 193 to 22 955 ng g-1). However, house dust provides a major contribution to human exposure due to the time spent there, much higher than in cars. © 2009 Elsevier Ltd. All rights reserved.

Ferreira J.A.,University of Aveiro | Azevedo N.F.,LEPAE | Azevedo N.F.,University of Minho | Vieira M.J.,University of Minho | And 4 more authors.
Carbohydrate Research | Year: 2010

With the intent of contributing to a carbohydrate-based vaccine against the gastroduodenal pathogen, Helicobacter pylori, we report here the structure of cell-surface mannans obtained from a virulent strain. Unlike other wild-type strains, this strain was found to express in good quantities this polysaccharide in vitro. Structural analysis revealed a branched mannan formed by a backbone of α-(1→6)-linked mannopyranosyl residues with approximately 80% branching at the O-2 position. The branches were composed of O-2-linked Man residues in both α- and β-configurations:{A figure is presented}. In addition, this strain also expressed cell-surface emblematic H. pylori lipopolysaccharides (LPS) containing partially fucosylated polyLacNAc O-chains. Affinity assays with polymyxin-B and concanavalin A revealed no association between the mannan and the LPS. The described mannans may be implicated in the mediation of host-microbial interactions and immunological modulation. © 2010 Elsevier Ltd. All rights reserved.

Simoes M.,LEPAE | Simoes L.C.,IBB Institute for Biotechnology And Bioengineering | Vieira M.J.,IBB Institute for Biotechnology And Bioengineering
LWT - Food Science and Technology | Year: 2010

Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin). The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry. © 2009 Elsevier Ltd. All rights reserved.

Apolinario A.,University of Porto | Sousa C.T.,University of Porto | Ventura J.,University of Porto | Costa J.D.,University of Porto | And 6 more authors.
Journal of Materials Chemistry A | Year: 2014

Highly ordered TiO2 nanotubes (NTs) were synthesized by electrochemical anodization of Ti foils. We investigated the effect of the Ti surface roughness (applying different pre-treatments prior to the anodization) on the length, growth rate and degree of self-organization of the obtained NT arrays. The mechanisms related to the TiO2 NT formation and growth were correlated not only with the corresponding anodization curves but also with their appropriate derivatives (1st order) and suitable integrated and/or obtained parameters, to reveal the onset and end of different electrochemical regimes. This enables an in-depth interpretation (and physical-chemical insight), for different levels of surface roughness and topographic features. We found that pre-treatments lead to an extremely small Ti surface roughness, offer an enhanced NT length and also provide a significant improvement in the template organization quality (highly ordered hexagonal NT arrays over larger areas), due to the optimized surface topography. We present a new statistical approach for evaluating highly ordered hexagonal NT array areas. Large domains with ideally arranged nanotube structures represented by a hexagonal closely packed array were obtained (6.61 μm2), close to the smallest grain diameter of the Ti foil and three times larger than those so far reported in the literature. The use of optimized pre-treatments then allowed avoiding a second anodization step, ultimately leading to highly hexagonal self-ordered samples with large organized domains at reduced time and cost. © 2014 the Partner Organisations.

Pires J.C.M.,LEPAE | Martins F.G.,LEPAE
Water, Air, and Soil Pollution | Year: 2012

This study aims to apply principal component analysis (PCA) to identify monitoring sites with similar variations of PM 10 concentrations in the London Air Quality Monitoring Network. This statistical methodology was applied to hourly average concentrations measured at 27 monitoring sites during the period from January 2000 to December 2009. The monitoring sites were selected according their efficiency in the study period (greater than 75% for each year). It was observed that the hourly average PM 10 concentrations were decreasing along the selected period at almost all monitoring sites. PCA was performed for each year, selecting the number of principal components (PCs) that had at least 95% of the original data variance. Analysing the frequency with which each pair of monitoring sites gave a significant contribution to the same PC, nine city areas with specific PM 10 behaviour were identified. Thus, monitoring sites with redundant measurements during the studied period were identified, being possible to remove them to decrease the costs relative to their maintenance or replace them to increase the monitored area. © Springer Science+Business Media B.V. 2011.

Discover hidden collaborations