Porto, Portugal
Porto, Portugal

Time filter

Source Type

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.


Sousa S.I.V.,LEPAE | Pires J.C.M.,LEPAE | Martins E.M.,State University of Rio de Janeiro | Fortes J.D.N.,State University of Rio de Janeiro | And 2 more authors.
Environment International | Year: 2012

The effects of air pollution on health have been studied worldwide. Given that air pollution triggers oxidative stress and inflammation, it is plausible that high levels of air pollutants cause higher number of hospitalisations. This study aimed to assess the impact of air pollution on the emergency hospitalisation for respiratory disease in Rio de Janeiro, Brazil. The study was divided in two parts: Part I specifically addressing the air pollution assessment and Part II addressing the health assessment. Accordingly, this Part II aimed to estimate the association between the concentrations of PM 10, SO 2 and CO observed in Rio de Janeiro and the number of emergency hospitalisations at a central hospital due to respiratory diseases. The pollutant concentrations were measured at two different sites in Rio de Janeiro, but the excess relative risks were calculated based on the concentrations observed at one of the sites, where limits were generally exceeded more frequently, between September 2000 and December 2005. A time series analysis was performed using the number of hospitalisations, divided in three categories (children until 1year old, children aged between 1 and 5years old and elderly with 65years old or more) as independent variable, the concentrations of pollutants as dependent variables and temperature, relative humidity, long term trend, and seasonality as confounders. Data were analysed using generalised additive models with smoothing for some of the dependent variables. Results showed an excess risk of hospitalisation for respiratory disease higher than 2% per 10μgm -3 increase in PM 10 concentrations for children under 5years old, of 2% per 10μgm -3 increase in SO 2 for elderly above 65years old and around 0.1% per 10μgm -3 increase in CO for children under 1year and elderly. Other studies have found associations that are in agreement with the results achieved in this study. The study suggests that the ambient levels of air pollutants experienced in Rio de Janeiro between 2000 and 2005 were linked to the number of hospitalisations for respiratory diseases among children and elderly. © 2012 Elsevier Ltd.


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.


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.


Oliveira P.N.,Federal University of Santa Catarina | Catarino M.,LEPAE | Oliveira Muller C.M.,Federal University of Santa Catarina | Brandao L.,LEPAE | And 4 more authors.
Journal of Applied Polymer Science | Year: 2014

Composite proton conducting membranes were prepared by doping the membrane, prepared by crosslinking poly(vinyl alcohol) with sulfosuccinic acid (SSA), with boehmite [aluminum oxyhydroxide or γ-AlO(OH)]. The effect of the SSA and boehmite content on the membrane performance was studied and the results showed that the values for the ion exchange capacity (IEC) of the membranes were in the range of 0.45-4.80 mmol g-1, the water content and the Young's modulus were dependent on the amount of SSA and nanoparticles. The proton conductivity was in the range of 10-4 to 10-2 S cm-1 at 25°C and was directly related to the quantity of sulfonate groups present in the membrane, while the hydrogen permeability at 30°C was in the range of 10-13 to 10-12 mol cm s -1 cm-2 bar. The proton exchange membrane fuel cell tests indicated that the composite membranes have good proton conductivity and very low hydrogen permeability. © 2013 Wiley Periodicals, Inc.


Khaddour I.A.,LEPAe | Bento L.S.M.,LEPAe | Ferreira A.M.A.,LEPAe | Ferreira A.M.A.,IBB Institute for Biotechnology And Bioengineering | Rocha F.A.N.,LEPAe
Surface Science | Year: 2010

Growth rates of sucrose crystallization from pure solutions of initial relative supersaturation levels between 0.094 and 0.181 were studied in agitated crystallizer at 313.13 K. Birth and spread model was applicable for the obtained growth rate data in this range of supersaturation and used to estimate the principal growth parameters. The estimated interfacial free energy varied inversely with supersaturation from 0.00842 to 0.00461 J/m2, respectively. The obtained kinetic coefficient changed with the initial supersaturation from 9.45 × 10- 5 to 2.79 × 10- 7 m/s. The corresponding radius of the 2D (two dimensional) critical nucleus varied from 7.47 × 10- 9to 1.46 × 10- 9 m. Predominance of surface integration or volume diffusion mechanism during the growth process was assessed using the calculated activation free energies of the 2D nucleation process. An acceptable confirmation of the calculated radius of the critical 2D nucleus was found using atomic force microscopy (AFM) technique. The calculated interfacial free energy between the saturated sucrose solution and the crystal surface was found to be 0.02325 J/m2. © 2010 Elsevier B.V. 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.


Gomes J.F.P.S.,LEPAE | Rocha S.,LEPAE | Pereira M.d.C.,LEPAE | Peres I.,LEPAE | And 3 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2010

A novel system to carry and protect epigallocatechin gallate (EGCG), an antioxidant from the green tea, is reported. The system consists of maltodextrin and gum arabic nanoparticles coated with egg-yolk l-α-phosphatidylcholine (Egg-PC)/stearylamine (SA) bilayers. In this study, the polysaccharide core was produced by homogenization followed by spray-drying. The lipid coating was performed by the lipid film hydration method. The polysaccharide core revealed negative zeta potential, which changed to opposite signs after lipid coating. The presence of lipid layers was evidenced by cryogenic-transmission (cryo-TEM) and scanning (cryo-SEM) electron microscopy studies. An increase in size was observed after lipid coating as determined by dynamic light scattering (DLS). Atomic force microscopy (AFM) demonstrated that the polysaccharide core provides high resistance to mechanical strength. The lipid/particle assemblies show high retention efficiency of EGCG at physiological pH, opening the possibility of their use for delivery and controlled release of tea catechins. © 2009 Elsevier B.V. All rights reserved.


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.


Campo M.C.,LEPAE | Magalhaes F.D.,LEPAE | Mendes A.,LEPAE
Journal of Membrane Science | Year: 2010

Carbon molecular sieve membranes (CMSM) were successfully prepared from cellophane paper by one single pyrolysis step. The influence of pyrolysis parameters on the membranes' structure, morphology and performance was examined through scanning electron microscopy, X-ray microanalysis, X-ray diffraction and monocomponent permeation experiments towards He, H2, Ar, N2, CO2, O2, CH4 and water vapor at 29.5 °C. The permeabilities reached a maximum for CMSM heated up to 550 °C, without significantly compromising selectivities. The soaking time at this temperature led to pore closing and, consequently, decrease in permeability and an enhancement in selectivity. These membranes were also considerably permeable to water vapor (1000 barrer), and very selective concerning H2O/CH4 (α = 921-7518) and H2O/N2 (α = 364-9936) separations. No aging effects were observed due to oxygen or water vapor exposure. The permselectivity of CMSM prepared up to 550 °C overtook the Robeson bound for polymeric membranes, especially regarding ideal selectivities of pairs O2/N2 (α = 13-18), H2/N2, H2/O2, H2/CH4 and H2/CO2. Therefore, they might be considered in relevant industrial applications such as separation of nitrogen from air and recovery of hydrogen from synthesis gas. © 2010 Elsevier B.V. All rights reserved.

Loading LEPAE collaborators
Loading LEPAE collaborators