Instituto Superior Of Educacao E Ciencias

Lisbon, Portugal

Instituto Superior Of Educacao E Ciencias

Lisbon, Portugal
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Santos H.A.F.A.,Instituto Superior Of Educacao E Ciencias
Acta Mechanica | Year: 2015

This paper addresses the development of a novel updated Lagrangian variational formulation and its associated finite element model for the geometrically nonlinear quasi-static analysis of cantilever beams. The formulation is based on an incremental complementary energy principle. The proposed finite element model only contains nodal bending moments as degrees of freedom. The model is used for the analysis of problems modeled by the so-called elastica theory. Numerical solutions satisfying all equilibrium equations in a strong sense can be obtained for arbitrarily large displacements and rotations. A Newton–Raphson method is adopted to trace the post-buckling response. Numerical results are presented and compared with those produced by the standard total Lagrangian two-node displacement-based finite element model. © 2014, Springer-Verlag Wien.

Martins F.,University of Lisbon | Santos S.,University of Lisbon | Ventura C.,University of Lisbon | Ventura C.,Instituto Superior Of Educacao E Ciencias | And 18 more authors.
European Journal of Medicinal Chemistry | Year: 2014

The disturbing emergence of multidrug-resistant strains of Mycobacterium tuberculosis (Mtb) has been driving the scientific community to urgently search for new and efficient antitubercular drugs. Despite the various drugs currently under evaluation, isoniazid is still the key and most effective component in all multi-therapeutic regimens recommended by the WHO. This paper describes the QSAR-oriented design, synthesis and in vitro antitubercular activity of several potent isoniazid derivatives (isonicotinoyl hydrazones and isonicotinoyl hydrazides) against H37Rv and two resistant Mtb strains. QSAR studies entailed RFs and ASNNs classification models, as well as MLR models. Strict validation procedures were used to guarantee the models' robustness and predictive ability. Lipophilicity was shown not to be relevant to explain the activity of these derivatives, whereas shorter N-N distances and lengthy substituents lead to more active compounds. Compounds 1, 2, 4, 5 and 6, showed measured activities against H37Rv higher than INH (i.e., MIC ≤ 0.28 μM), while compound 9 exhibited a six fold decrease in MIC against the katG (S315T) mutated strain, by comparison with INH (i.e., 6.9 vs. 43.8 μM). All compounds were ineffective against H37RvINH (ΔkatG), a strain with a full deletion of the katG gene, thus corroborating the importance of KatG in the activation of INH-based compounds. The most potent compounds were also shown not to be cytotoxic up to a concentration 500 times higher than MIC. © 2014 Elsevier Masson SAS. All rights reserved.

Martins F.,University of Lisbon | Leitao R.E.,Polytechnic Institute of Lisbon | Ventura M.C.,University of Lisbon | Ventura M.C.,Instituto Superior Of Educacao E Ciencias | And 2 more authors.
Journal of Molecular Liquids | Year: 2012

Refractive indices, n D, and densities, ρ, at 298.15 K were measured for the ternary mixture methanol (MeOH)/propan-1-ol (1-PrOH)/acetonitrile (MeCN) for a total of 22 mole fractions, along with 18 mole fractions of each of the corresponding binary mixtures, methanol/propan-1-ol, propan-1-ol/acetonitrile and methanol/acetonitrile. The variation of excess refractive indices and excess molar volumes with composition was modeled by the Redlich-Kister polynomial function in the case of binary mixtures and by the Cibulka equation for the ternary mixture. A thermodynamic approach to excess refractive indices, recently proposed by other authors, was applied for the first time to ternary liquid mixtures. Structural effects were identified and interpreted both in the binary and ternary systems. A complex relationship between excess refractive indices and excess molar volumes was identified, revealing all four possible sign combinations between these two properties. Structuring of the mixtures was also discussed on the basis of partial molar volumes of the binary and ternary mixtures. © 2012 Elsevier B.V. All rights reserved.

Pinheiro L.M.V.,University of Lisbon | Ventura M.C.M.M.,Instituto Superior Of Educacao E Ciencias | Moita M.L.C.J.,University of Lisbon
Journal of Molecular Liquids | Year: 2010

Quantitative Structure-Property Relationship methodology was applied successfully to experimental molar transition energies of quinoline, published before, in order to achieve a better understanding about the predominant quinoline-solvent interactions. Internal and external model validations were performed showing a high predictive ability of the selected multiple linear relationship. The wavenumbers of maximum absorbance of five dyes UV-vis spectra in methanol/dimethylformamide, propan-1-ol/dimethylformamide and pentan-1-ol/dimethylformamide mixtures, and in pure solvents, were experimentally determined, at 298.15 K, with the aim of calculating the Kamlet and Taft solvatochromic parameters (π, α and β). Refractive indices of those mixtures were also calculated, to evaluate the Lorentz-Lorenz function values, g(nD). The chosen solvatochromic response model of quinoline suggests the dominance of the dipolarity/polarizability (π) and the basicity (β) parameters followed by the ET N one (predominantly a measure of the solvent acidity). The former parameter contributes to a higher stabilization of the ground state and the two latter ones to a greater stabilization of the quinoline Frank-Condon excited state. © 2010 Elsevier B.V. All rights reserved.

Moita M.-L.C.J.,University of Lisbon | Reis M.C.,University of Lisbon | Reis M.C.,Instituto Superior Of Educacao E Ciencias | Santos A.F.S.,University of Lisbon | Lampreia I.M.S.,University of Lisbon
Journal of Chemical Thermodynamics | Year: 2015

Given the importance that enthalpic and entropic contributions have in the interplay between thermodynamics and self-assembly of aqueous amphiphile systems, the energetic characterisation of the system {water + 1-propoxypropan-2-ol (1-pp-2-ol)} at T = 298.15 K was made by directly measuring excess partial molar enthalpies of 1-pp-2-ol and water, over the entire composition range, at T = 298.15 K and atmospheric pressure. Derivatives of the partial molar properties with respect to the composition are used to improve the understanding of molecular interactions in the water-rich region. The present results were compared with those for the well-studied system {water + 2-butoxyethanol (nC4E1)}, the two amphiphiles being structural isomers. © 2015 Elsevier Ltd. All rights reserved.

Rafols C.,University of Barcelona | Bosch E.,University of Barcelona | Ruiz R.,Sirius Analytical Ltd. | Box K.J.,Sirius Analytical Ltd. | Ventura C.,Instituto Superior Of Educacao E Ciencias
Journal of Chemical and Engineering Data | Year: 2012

Hydrophobicity values (log P o/w) determined both by potentiometry and by the conventional shake-flask method and aqueous pK a values obtained by potentiometry for seven isoniazid and nine benzimidazole derivatives are presented. Several of these compounds have strong hydrophilic or hydrophobic character, and some of them show two or more ionizable sites, sometimes very acidic or very basic. These facts have compelled us to work near the limits of the potentiometric technique, and therefore, a critical evaluation of the results obtained in these extreme working conditions is presented. Particularly, details about the potentiometric determination of log P o/w values of the most hydrophilic and most hydrophobic compounds are clearly described. © 2011 American Chemical Society.

Ventura C.,University of Lisbon | Ventura C.,Instituto Superior Of Educacao E Ciencias | Latino D.A.R.S.,New University of Lisbon | Latino D.A.R.S.,University of Lisbon | Martins F.,University of Lisbon
European Journal of Medicinal Chemistry | Year: 2013

The performance of two QSAR methodologies, namely Multiple Linear Regressions (MLR) and Neural Networks (NN), towards the modeling and prediction of antitubercular activity was evaluated and compared. A data set of 173 potentially active compounds belonging to the hydrazide family and represented by 96 descriptors was analyzed. Models were built with Multiple Linear Regressions (MLR), single Feed-Forward Neural Networks (FFNNs), ensembles of FFNNs and Associative Neural Networks (AsNNs) using four different data sets and different types of descriptors. The predictive ability of the different techniques used were assessed and discussed on the basis of different validation criteria and results show in general a better performance of AsNNs in terms of learning ability and prediction of antitubercular behaviors when compared with all other methods. MLR have, however, the advantage of pinpointing the most relevant molecular characteristics responsible for the behavior of these compounds against Mycobacterium tuberculosis. The best results for the larger data set (94 compounds in training set and 18 in test set) were obtained with AsNNs using seven descriptors (R2 of 0.874 and RMSE of 0.437 against R2 of 0.845 and RMSE of 0.472 in MLRs, for test set). Counter-Propagation Neural Networks (CPNNs) were trained with the same data sets and descriptors. From the scrutiny of the weight levels in each CPNN and the information retrieved from MLRs, a rational design of potentially active compounds was attempted. Two new compounds were synthesized and tested against M. tuberculosis showing an activity close to that predicted by the majority of the models. © 2013 Elsevier Masson SAS. All rights reserved.

Martins F.,University of Lisbon | Moreira L.,University of Lisbon | Moreira L.,Instituto Superior Of Educacao E Ciencias | Nunes N.,Polytechnic Institute of Lisbon | Leitao R.E.,Polytechnic Institute of Lisbon
Journal of Thermal Analysis and Calorimetry | Year: 2010

Solution enthalpies of 1-bromoadamantane, 1-adamantanol, and 2-adamantanone in a large set of protic and aprotic solvents are reported at 298.15 K. Solvent effects on the solution processes of these solutes are analyzed in terms of a modified TAKA equation, involving δcav h s as the cavity term. The nature and magnitude of the major interactions which influence these processes are assessed and discussed in terms of the solutes' characteristics. New insights on the solution processes under scrutiny are presented. © 2010 Akadémiai Kiadó, Budapest, Hungary.

Bras P.,Instituto Superior Of Educacao E Ciencias | Miranda G.L.,University of Lisbon
Iberian Conference on Information Systems and Technologies, CISTI | Year: 2013

Liaw's attitude questionnaire towards computers and the World Wide Web (WWW), first published in 2002, has revealed good internal consistency but factorial problems over time. 'Attitudes' can predict people's behavior in certain situations, although the relationship between attitude and behavior is complex and multidimensional. Having reliable and valid instruments to measure variables is an essential condition for the credibility of a research. Thus, we developed a study to determine the psychometric characteristics of this questionnaire applied to a sample of Portuguese teachers. Based on this study, other professionals may apply this instrument safely. It should be noted that the validation of a measure instrument for the social sciences is an ongoing process. In other words, validation is always needed when applying the instruments on new samples. The accumulation of data is crucial to determine the stability and credibility of the instrument, evaluating results and leading to its improvement. © 2013 AISTI.

Reis M.,University of Lisbon | Moreira L.,University of Lisbon | Moreira L.,Instituto Superior Of Educacao E Ciencias | Nunes N.,Polytechnic Institute of Lisbon | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2012

Solution enthalpies of adamantan-1-ol, 2-methylbutan- 2-ol, and 3-methylbutan-1-ol have been measured at 298.15 K, in a set of 16 protogenic and non-protogenic solvents. The identification and quantification of solvent effects on the solution processes under study were performed using quantitative-structure property relationships. The results are discussed in terms of solute-solvent-solvent interactions and also in terms of the influence of compound's size and position of its hydroxyl group. © Akadémiai Kiadó, Budapest, Hungary 2011.

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