Browsing by Issue Date, starting with "2018-02"
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- From motivation and self-structure to a decision support framework for online social networksPublication . Antunes, Francisco; Freire, Manuela; Costa, João PauloData collected from online social networks offers new possibilities for supporting organizations’ daily activities. It is also common knowledge that the opinion exchange in online social networks provides a decisive contribution in decision making. It is, thus, necessary to review and bare present the motivations by which people engage in online social network and the ways in which firms can make use of such motivations in order to take advantage of online social networks as information sources for decisionmaking support. To do so, the authors of this chapter developed the decision-support social networks to extract such information, which encompasses the intertwined use of human interaction and network structure by combining human capabilities, social network analysis (SNA), and automatic data mining. In this chapter, a brief summary of the performed case studies over the proposed information model is also presented.
- A new high performance method for determining the parameters of PV cells and modules based on guaranteed convergence particle swarm optimizationPublication . Nunes, H.G.G.; Pombo, José Álvaro Nunes; Mariano, S.; Calado, M. do Rosário; Felippe de Souza, J.A.M.Determining the mathematical model parameters of photovoltaic (PV) cells and modules represents a great challenge. In the last few years, several analytical, numerical and hybrid methods have been proposed for extracting the PV model parameters from datasheets provided by the manufacturers or from experimental data, although it is difficult to determine highly reliable solutions quickly and accurately. In this paper, we propose a new method for determining the PV parameters of both the single-diode and the double-diode models, based on the guaranteed convergence particle swarm optimization (GCPSO), using experimental data under different operating conditions. The main advantage of this method is its ability to avoid premature convergence in the optimization of complex and multimodal objective functions, such as the function that determines PV parameters. To validate performance, the GCPSO method was compared with several analytical, numerical and hybrid methods found in the literature. This validation considered three different case studies. The first two are important reference case studies in the literature and have been widely used by researchers. The third was performed in an experimental environment, in order to test the proposed method under a real implementation. The proposed methodology can find highly accurate solutions while demanding a reduced computational cost. Comparisons with other published methods demonstrate that the proposed method produces very good results in the extraction of the PV model parameters.
- Generalized Trichotomies: robustness and global and local invariant manifoldsPublication . Costa, Cristina Maria Gomes Tomás da; Bento, António Jorge GomesIn a Banach space, given a differential equation v′(t) = A(t)v(t), with an initial condition v(s) = vs and that admits a generalized trichotomy, we studied which type of conditions we need to impose to the linear perturbations B so that v′(t) = [A(t) + B(t)] v(t) continues to admit a generalized trichotomy, that is, we studied the robustness of generalized trichotomies. In the same way, it was also the aim of our work the study of a differential equation with another type of nonlinear perturbations, v′(t) = A(t)v(t) + f(t, v). We sought conditions to impose on the function f so that the new perturbed equation would admit a global Lipschitz invariant manifold as well as the necessary conditions for the existence of local Lipschitz invariant manifolds.
- Caracterização e Análise dos Processos Produtivos em Empresas AgroalimentaresPublication . Gaspar, Pedro Dinis; Elias, M.; Pereira, C. D.; Andrade, Luís P.; Pinheiro, R.; Paiva, Teresa; Soares, C.; Gândara, J.; Henriques, M.; Laranjo, Marta; Potes, Maria Eduarda; Santos, A. C. Agulheiro; Santos, F. C.; Silva, Pedro Dinho da; Nunes, J.; Coutinho, P.; Carneiro, J.; Várzea, J. P.; Velho, Manuela Vaz; Araújo, M. A.; Ribeiro, M.; Santos, J.; Matias, JoãoAtravés de um diagnóstico inicial baseado na análise do conhecimento, informação existente, recolha de informação e medição de parâmetros num conjunto de empresas (60) dos subsetores dos produtos cárneos, hortofrutícolas, lácteos e panificação apresenta-se através do presente relatório a caracterização dos processos e atividades produtivas em empresas do setor agroalimentar. Executando uma análise técnica ao estado da arte, através do estudo da organização das atividades produtivas, nível tecnológico e tendências no desenvolvimento de produtos, permite-se de acordo com a informação disponível realizar uma comparação das empresas em análise com a performance da indústria, globalmente, por região ou setor de atividade. Verifica-se através da análise ao presente relatório, quais os fatores que permitem a criação de valor no setor agroindustrial de uma forma contínua para a cadeia de valor organizacional. Por outro lado, entre os diversos pontos a melhorar, considerando as organizações em análise, destaca-se a cultura de inovação e a digitalização dos processos de produção (Indústria 4.0).
- Mix design of structural lightweight self-compacting concrete incorporating coarse lightweight expanded clay aggregatesPublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira de; Pereira, Sandrine de FreitasThis paper reports an experimental study that aimed to define the parameters for the mix design of structural lightweight self-compacting concrete (LWSCC) incorporating coarse lightweight expanded clay aggregates and natural sand. The starting point was the methodology proposed by Nepomuceno et al. (2014) for normal density self-compacting concrete (SCC). The necessary modifications were evaluated and new correlations obtained to support the definition of the mix design parameters. It was concluded that the coarse aggregates reference curve, as well as the mortar phase flow properties proposed by Nepomuceno et al. (2012) for the SCC, are adequate to produce LWSCC. Correlations to quantify the volume of coarse lightweight aggregates (Vg) are presented. It was shown that Vg depends on the mortar phase proportions, concrete workability properties, concrete compressive strength and concrete oven-dry density. The analysis of dynamic and static segregation shows a satisfatory performance with a uniform distribution of lightweight aggregates.
- Development of new antiepileptic drug candidates: a set of lamotrigine-related compoundsPublication . Matias, Mariana Ruivo; Alves, Gilberto Lourenço; Silvestre, Samuel Martins; Ferreira, Amílcar Celta Falcão RamosEpilepsy is one of the most common, chronic and serious neurological disorder, affecting million people worldwide. This brain disorder is characterised by recurrent spontaneous seizures, which have a considerable impact in the patients’ quality of life. The pharmacological therapy has been, and is likely to remain, the mainstay of treatment for this disorder. Although a large number of new antiepileptic drugs (AEDs) has been introduced into the market in the last years, about 30-40% of epileptic patients are still inadequately controlled by standard drug therapy. For this reason, it continues to be important to develop new and improved chemical entities through which epilepsy could be effectively controlled. In this context, the main objective of the present work was to discover new lead compounds with anticonvulsant properties for further development as AEDs. To achieve this goal, fifty dihydropyrimidin(thi)ones [DHPM(t)s] were synthesized through the Biginelli reaction, which consists in a one-pot cyclocondensation reaction among an aldehyde, a β-ketoester/acetylacetone and urea or thiourea. The products were purified and characterised by infrared and 1H- and 13C-nuclear magnetic resonance spectroscopy. High resolution mass spectrum was also obtained for the novel compounds. Afterwards, the anticonvulsant activity of the compounds was evaluated against electrically [maximal electroshock seizure (MES) test] and chemically [subcutaneous pentylenetetrazole (scPTZ) test] induced seizures in rodent models. The initial anticonvulsant screening was performed in CD-1 mice (n = 4/group) at 30 min and 4 h after the intraperitoneal administration of 30, 100 and 300 mg/kg of each compound. The investigated compounds were also evaluated in mice for neuromotor impairment (as a surrogate of minimal neurological deficit) on the rotarod performance test. Then, selected compounds previously identified as anticonvulsants in mice at the minimum dose tested were further assessed in Wistar rats (n = 4/group) at 30 min, 2 h and 4 h after the oral administration of 30 mg/kg. Additionally, the fifty DHPM(t)s were evaluated for their in vitro cytotoxicity in rat mesencephalic dopaminergic (N27), human hepatocellular carcinoma (HepaRG), human colorectal adenocarcinoma (Caco-2) and normal human dermal fibroblasts (NHDF) cell lines, through the well-established 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at the concentration of 30 μM. Moreover, as the efficacy of a molecule is strongly dependent on its pharmacokinetics, several kinetic properties were also investigated in in vitro and in silico models. Thus, all compounds were subjected to a set of in vitro screening assays performed on a cell line overexpressing the drug efflux transporter P-glycoprotein (MDCK-MDR1 cells) and on two models of parallel artificial membrane permeability assay (PAMPA) preditive of the apparent permeability (Papp) through intestinal membrane (intestinal PAMPA model) and blood-brain barrier (PAMPA-BBB model). Lastly, several physicochemical properties of the compounds were also calculated in silico and a set of pharmacokinetic and toxicity properties were estimated employing the new computational tool, pkCSM. The target molecules that were synthesized were mainly selected based on the structure of clinically relevant AEDs, in particular the structure of lamotrigine, aiming to discover new candidates for the development of improved AEDs. The majority of the chemical reactions occurred fastly and the products were obtained in good yields. The synthetic procedure used was also extended using additional specific reagents, being the respective products, which are new to the best of our knowledge, successfully synthesized. Due to practical considerations, only forty-two compounds (twenty-eight urea derivatives and fourteen thiourea derivatives) proceeded to in vivo experiments. The results of the initial pharmacological screening in mice revealed anticonvulsant protection in the MES model for twenty-four compounds showed anticonvulsant protection in the MES model, being nine of them active at the lowest dose tested (30 mg/kg). Structurally, the most promising compounds present smaller chains at the C5 of the dihydropyrimidine ring and an unsubstituted phenyl or a para-tolyl ring at the C4. In addition, the thiourea analogues also presented slightly increased anticonvulsant activity comparing with the corresponding urea analogues. The results of the minimal neuromotor impairment obtained through the rotarod assay showed that approximately 52% of the compounds are less toxic than lamotrigine, carbamazepine and phenytoin. Compounds MM 17, MM 19 and MM 83 also protected against MES-induced seizures in 50-75% of rats after the oral administration of 30 mg/kg. Furthermore, the most active compounds did not show notable cytotoxicity in in vitro experiments conducted in the several cell lines (relative cell proliferation higher than 50% at 30 μM), which can be relevant due to the fact that the toxicity is a common problem of the available AEDs. The data obtained showed that 82% of the investigated compounds are expected to have good intestinal permeability (Papp > 1.1×10-6 cm/s), and 66% of which good brain penetration (Papp > 2.0×10-6 cm/s), which can suggest a high passive transcellular permeability. In both cases, thiourea derivatives presented higher permeability values than the respective urea analogues, which can be associated with their higher lipophilicity. This finding can explain, at least in part, the higher activity of the thiourea derivatives in the anticonvulsant screening after both intraperitoneal and oral administrations. In addition, 44% of the compounds did not significantly modulate (inhibit or induce) P-glycoprotein at 10 and 50 μM. This is an interesting finding since P-glycoprotein is physiologically expressed in several tissues and organs relevant from a pharmacokinetics perspetive. Finally, in silico studies indicated that all compounds respect the Lipinski’s rule-of-five, suggesting that they possess favourable properties that fulfil the druglikeness criteria. The pkCSM in silico tool also estimated that the DHPM(t)s have good human intestinal absorption (67.73-93.91%) and an apparent volume of distribution at the steady-state in the same range of values of the AEDs. The in silico predictions also suggested a low plasma protein binding percentage for the target compounds, which is considered to be therapeutically favourable, minimizing the risk of drug interactions. These results corroborate those obtained with the intestinal PAMPA assay that showed that probably none of the tested compounds have a binding to plasma proteins higher than 90% (Papp ≤ 1.0×10−5 cm/s). The thiourea derivatives were also predicted as compounds that permeate better through biological barriers (e.g., Caco-2 cell monolayers and blood-brain barrier), similarly to the observed in the experimental PAMPA assays. However, the prediction model suggested that 14% of the urea derivatives have tendency for cytochrome P450 inhibition versus 36% of the thiourea derivatives. On the other hand, concerns on the disruption of normal liver function were predicted for half of the compounds. Overall, the set of studies carried out provide new information about the anticonvulsant activity of this class of heterocycles, along with pharmacokinetic and toxicity data. More than half of the investigated molecules showed anticonvulsant protection against electrically-induced seizures (MES model), confirming the interest of the pharmacophoric model for the design of new anticonvulsant agents. The data gathered here allowed to identify important structural features of this attractive scaffold that can be responsible for the anticonvulsant activity, which should be maintained or better explored in order to produce more active analogues in further hit-to-lead optimization. However, the results presented in this thesis are just the “tip of the iceberg” in the discovery and development of the DHPM(t)s as potential AEDs.
- Five-year follow-up of participants diagnosed with chronic airflow obstruction in a South African Burden of Obstructive Lung Disease (BOLD) surveyPublication . Allwood, Brian; Gillespie, R; Bateman, Mary; Olckers, Helena; Barata, Luis Taborda; Calligaro, Gregory L; van Zyl-Smit, Richard; Cooper, Christopher B; Beyers, N; Bateman, EricBackground. A community-based prevalence survey performed in two suburbs in Cape Town, South Africa (SA), in 2005, using the international Burden of Obstructive Lung Disease (BOLD) method, confirmed a prevalence of chronic airflow obstruction (CAO) in 23.1% of adults aged >40 years. Objectives. To study the clinical course and prognosis over 5 years of patients with CAO identified in the 2005 survey. Methods. Patients with CAO in 2005 were invited to participate. Standard BOLD and modified questionnaires were completed. Spirometry was performed using spirometers of the same make as in 2005. Results. Of 196 eligible participants from BOLD 2005, 45 (23.0%) had died, 8 from respiratory causes, 10 from cardiovascular causes and 6 from other known causes, while in 21 cases the cause of death was not known. On multivariate analysis, only age and Global initiative for Obstructive Lung Disease (GOLD) stage 4 disease at baseline were significantly associated with death. Of the 151 survivors, 11 (5.6% of the original cohort) were unavailable and 33 (16.8%) declined or had medical exclusions. One hundred and seven survivors were enrolled in the follow-up study (54.6%, median age 63.1 years, 45.8% males). Post-bronchodilator spirometry performed in 106 participants failed to confirm CAO, defined as a forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio of <0.7, in 16 participants (15.1%), but CAO was present in 90. The median decline in FEV1 was 28.9 mL/year (interquartile range –54.8 - 0.0) and was similar between GOLD stages. The median total decline in FVC was 75 mL, and was significantly greater in GOLD stage 1 (–350 mL) than in stages 2 or 3 (–80 mL and +140 mL, respectively; p<0.01). Fifty-eight participants with CAO in 2005 (64.4%) remained in the same GOLD stage, while 21 (23.3%) deteriorated and 11 (12.2%) improved by ≥1 stage. Only one-third were receiving any treatment for chronic obstructive pulmonary disease (COPD). Conclusions. The prevalence, morbidity and mortality of CAO and COPD in SA are high and the level of appropriate treatment is very low, pointing to underdiagnosis and inadequate provision of and access to effective treatments and preventive strategies for this priority chronic non-communicable disease.
- Internal marketing and organisational performance of SMEs in the EDV industrial sectorPublication . Rodrigues, Ricardo; Sousa, João Pedro; Krot, KatarzynaFocusing on the industrial sector, this research aims to identify conditions for the implementation of internal marketing concepts among employees and its impact on the organisational performance. Only one study was found simultaneously integrating the two constructs. It concerned the cork processing industry alone, yet considered expanding the efforts – namely, using qualitative exploratory research in the form of 10 in-depth interviews based on a script of generally open questions – to the entire industry in the Portuguese region between rivers Douro and Vouga. The unit of analysis was constructed considering distinct features as well as activity criteria and the geographic location, thus ensuring the necessary heterogeneity. The results inform about the awareness of the internal marketing conceptualisation. The research found that all analysed enterprises had more or less structured model frames and worked with the conceptualisation of the guidance for the internal market, a strategic concern, and in some instances, this concept was an organisational desideratum in the sector. In addition to the lapse of the research according to a qualitative paradigm of exploratory nature, the main limitation is the need for objective sustainably of the results obtained through future quantitative studies to promote an integrated triangulation of their outcomes. The research allowed identifying the companies that use organisational models conducive to the individual well-being of employees and facilitating the desired orientation to the market.
- Optimal control of the customer dynamics based on marketing policyPublication . Rosa, Silvério; Rebelo, P.; Silva, C. M.; Alves, Helena; Carvalho, Pedro Guedes deWe consider an optimal control problem for a non-autonomous model of ODEs that describes the evolution of the number of customers in some firm. Namely we study the best marketing strategy. Considering a L2 cost functional, we establish the existence and uniqueness of optimal solutions, using an inductive argument to obtain uniqueness on the whole interval from local uniqueness. We also present some simulation results, based on our model, and compare them with results we obtain for an L1 cost functional. For the L1 cost functional the optimal solutions are of bang-bang type and thus easier to implement, because at every moment possible actions are chosen from a finite set of possibilities. For the autonomous case of L2 problem, we show the effectiveness of the optimal control strategy against other formulations of the problem with simpler controls.
- Recent advances on antimicrobial wound dressing: A reviewPublication . Simões, Déborah; Miguel, Sónia P.; Ribeiro, MP.; Coutinho, Paula Isabel Teixeira Gonçalves; Mendonça, António; Correia, Ilídio Joaquim SobreiraSkin and soft tissue infections (SSTIs) have high rates of morbidity and mortality associated. Despite the successful treatment of some SSTIs, those affecting the subcutaneous tissue, fascia, or muscle delay the healing process and can lead to life-threatening conditions. Therefore, more effective treatments are required to deal with such pathological situations. Recently, wound dressings loaded with antimicrobial agents emerged as viable options to reduce wound bacterial colonization and infection, in order to improve the healing process. In this review, an overview of the most prominent antibacterial agents incorporated in wound dressings along with their mode of action is provided. Furthermore, the recent advances in the therapeutic approaches used in the clinic and some future perspectives regarding antibacterial wound dressings are also discussed.