High Institute of Engineering of Lisbon
High Institute of Engineering of Lisbon
Sargaco B.,High Institute of Engineering of Lisbon |
Serra C.,High Institute of Engineering of Lisbon |
Vasco E.,National Health Institute Dr Ricardo Jorge
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment | Year: 2017
Cyclamate is widely used as intense sweetener in the European Union. The absence of a maximum limit for the use of cyclamate in tabletop sweeteners and the growing demand for this type of product highlights the importance of developing robust analytical methods for the determination of its content to understand if the consumption of tabletop sweeteners can have a negative impact on human health. The present work aimed at the optimisation and validation of an high-performance liquid chromatography (HPLC) analytical method for cyclamate determination in tabletop sweeteners based on the procedure of European Standard EN 12857. The validated method was then applied to the determination of this sweetener in different types of tabletop sweeteners (liquid, powder and tablets). Both standards and samples solutions were submitted to a derivatisation procedure which converted cyclamate to N,N-dichlorocyclohexylamine. The derivatised product was separated and quantified using a reversed-phase column, a mobile phase composed of water (20%) and methanol (80%), isocratic flow of 1 ml min–1, and detection by ultraviolet spectrophotometry at a wavelength of 314 nm. The analytical method was internally validated according to the following validation parameters: working range, linearity, limits of detection and quantification, sensitivity, precision (repeatability and intermediate precision), and uncertainty. This method proved to be specific and selective for the determination of this sweetener, showing repeatability, RSDr ≤ 3%, intermediate precision, RSDR ≤ 3.3%, and recovery rates from 92% to 108% for the different tabletop sweeteners. The method uncertainty was 9.4%. The concentration of cyclamate in the samples varied significantly, from 2.9% to 73.9%, which demonstrated that a possible excessive consumption of one of the analysed sweeteners can lead to exceeding the acceptable daily intake for cyclamate. © 2017 Informa UK Limited, trading as Taylor & Francis Group
Carvalho A.,High Institute of Engineering of Lisbon |
Pereira Dos Santos C.,University of Lisbon |
Dias C.,High Institute of Engineering of Lisbon |
Coelho F.,University of Évora |
And 3 more authors.
Theoretical Computer Science | Year: 2014
We show that a self-generated set of combinatorial games, S, may not be hereditarily closed but, strong self-generation and hereditary closure are equivalent in the universe of short games. In , the question "Is there a set which will give a non-distributive but modular lattice?" appears. A useful necessary condition for the existence of a finite non-distributive modular ℒ(S) is proved. We show the existence of S such that L(S) is modular and not distributive, exhibiting the first known example. More, we prove a Representation Theorem with Games that allows the generation of all finite lattices in game context. Finally, a computational tool for drawing lattices of games is presented. © 2014 Elsevier B.V. All rights reserved.
Branco A.,University of Évora |
Fialho A.,University of Évora |
Salvador C.,University of Évora |
Candeias A.,University of Évora |
And 5 more authors.
Science, Technology and Cultural Heritage - Proceedings of the 2nd International Congress on Science and Technology for the Conservation of Cultural Heritage, 2014 | Year: 2014
In paintings the characterization of proteic binders is of great interest, since it is an important source of information for conservation and restoration practices. Some studies suggest that the organic materials used in this type of art work has been widely applied as adhesives and binders in coating layers of paintings. The proteinaceous materials such as animal glues require a special attention given the suffering degradation over time, influenced by physical, chemical and biological factors. The aim of this work is the characterisation and purification of two animal glues (rabbit fur and fish) that are commonly used as binders in easel paintings. The animal glues revealed a polysaccharide content and trace of lipids, being mainly constituted by a mix of proteins. The use of native-PAGE, spectroscopy and chromatographic techniques allowed the characterisation and purification of the proteic binders, promoting a better knowledge about this type of animal adhesives used in easel paintings. © 2014 Taylor & Francis Group, London.
Bernardo M.,High Institute of Engineering of Lisbon |
Santos A.,High Institute of Engineering of Lisbon |
Cantinho P.,High Institute of Engineering of Lisbon |
Minhalma M.,High Institute of Engineering of Lisbon |
Minhalma M.,University of Lisbon
Water Research | Year: 2011
Wastewater from cork processing industry present high levels of organic and phenolic compounds, such as tannins, with a low biodegradability and a significant toxicity. These compounds are not readily removed by conventional municipal wastewater treatment, which is largely based on primary sedimentation followed by biological treatment. The purpose of this work is to study the biodegradability of different cork wastewater fractions, obtained through membrane separation, in order to assess its potential for biological treatment and having in view its valorisation through tannins recovery, which could be applied in other industries. Various ultrafiltration and nanofiltration membranes where used, with molecular weight cut-offs (MWCO) ranging from 0.125 to 91 kDa. The wastewater and the different permeated fractions were analyzed in terms of Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Phenols (TP), Tannins, Color, pH and Conductivity. Results for the wastewater shown that it is characterized by a high organic content (670.5-1056.8 mg TOC/L, 2285-2604 mg COD/L, 1000-1225 mg BOD/L), a relatively low biodegradability (0.35-0.38 for BOD5/COD and 0.44-0.47 for BOD20/COD) and a high content of phenols (360-410 mg tannic acid/L) and tannins (250-270 mg tannic acid/L). The results for the wastewater fractions shown a general decrease on the pollutant content of permeates, and an increase of its biodegradability, with the decrease of the membrane MWCO applied. Particularly, the permeated fraction from the membrane MWCO of 3.8 kDa, presented a favourable index of biodegradability (0.8) and a minimized phenols toxicity that enables it to undergo a biological treatment and so, to be treated in a municipal wastewater treatment plant. Also, within the perspective of valorisation, the rejected fraction obtained through this membrane MWCO may have a significant potential for tannins recovery. Permeated fractions from membranes with MWCO lower than 3.8 kDa, presented a particularly significant decline of organic matter and phenols, enabling this permeates to be reused in the cork processing and so, representing an interesting perspective of zero discharge for the cork industry, with evident environmental and economic advantages. © 2010 Elsevier Ltd.
Rodrigues D.B.,New University of Lisbon |
Da Silva Pereira P.J.,New University of Lisbon |
Da Silva Pereira P.J.,High Institute of Engineering of Lisbon |
Limao-Vieira P.M.,New University of Lisbon |
Maccarini P.F.,Duke University
Proceedings of the 8th IASTED International Conference on Biomedical Engineering, Biomed 2011 | Year: 2011
An analytical solution given by Bessel series to the transient and one-dimensional (1D) bioheat equation in a multilayer region with spatial dependent heat sources is derived. Multilayer regions with 1D Cartesian, cylindrical or spherical geometries and composed of different types of biological tissues characterised by temperature-invariant physiological parameters are considered. Boundary conditions of first, second and third kinds to the temperature at the inner and outer surfaces are also assumed. In this work, the bioheat transfer model is applied to obtain the temperature profiles in a tumor bed and a surrounding healthy tissue using two spatial dependent heat source terms to simulate a magnetic fluid hyperthermia technique in the cancer treatment. The influence of these two heat sources, described by polynomial and exponential functions, on temperature is investigated.
Lopes N.D.,High Institute of Engineering of Lisbon |
Lopes N.D.,New University of Lisbon |
Pereira P.J.S.,High Institute of Engineering of Lisbon |
Pereira P.J.S.,New University of Lisbon |
Trabucho L.,New University of Lisbon
International Journal for Numerical Methods in Fluids | Year: 2012
An improved class of Boussinesq systems of an arbitrary order using a wave surface elevation and velocity potential formulation is derived. Dissipative effects and wave generation due to a time-dependent varying seabed are included. Thus, high-order source functions are considered. For the reduction of the system order and maintenance of some dispersive characteristics of the higher-order models, an extra O(μ 2n+2) term (n ∈ ℕ) is included in the velocity potential expansion. We introduce a nonlocal continuous/discontinuous Galerkin FEM with inner penalty terms to calculate the numerical solutions of the improved fourth-order models. The discretization of the spatial variables is made using continuous P 2 Lagrange elements. A predictor-corrector scheme with an initialization given by an explicit Runge-Kutta method is also used for the time-variable integration. Moreover, a CFL-type condition is deduced for the linear problem with a constant bathymetry. To demonstrate the applicability of the model, we considered several test cases. Improved stability is achieved. © 2011 John Wiley & Sons, Ltd.