Browsing by Issue Date, starting with "2017-03"
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- Bioactivity gradients of cytoprotective and anticancer catechins in skin: Simulation studies for the design of controlled release systemsPublication . Silva, João; Videira, Paula; Lagoa, RicardoDermal delivery of catechins may be an effective approach for protection of skin against inflammation, aging and cancer caused by exposure to radiation and environmental toxicants. Catechins are flavonoid-type polyphenols showing capacity to attenuate UV-induced skin injury, carcinogenesis and melanoma metastasis, but the prevalence of beneficial effects depends on compound concentration. In this work, catechin penetration through the skin was simulated to predict the concentration in different layers: stratum corneum, viable epidermis and dermis. By combining these results with expected dose-effect relationships of the compounds, bioactivity profiles were calculated for relevant skin regions. Since the concentration dependences of catechin capacities to protect dermal fibroblasts and to inhibit melanoma cells (data aggregated from published literature) follow different types of dose-effect curves, bioactivity profiles in the skin can be different, even for the same delivery conditions. This method allows to estimate the delivery conditions (time and concentrations) required to achieve the desired biological/pharmacological activities at critical skin strata, namely, viable epidermis and dermis where metastatic melanoma cells and susceptible fibroblasts localize. The work suggests a framework to support the rational design of controlled release systems of topically applied bioactive compounds in therapeutic and investigative delivery.
- What is an ideal a zero-class of?Publication . Martins-Ferreira, Nelson; Montoli, A.; Ursini, A.; Linden, T. Van derWe characterise, in pointed regular categories, the ideals as the zero-classes of surjective relations. Moreover, we study a variation of the Smith is Huq condition: two surjective left split relations commute as soon as their zero-classes commute.
- Fundamental solutions of the time fractional diffusion-wave and parabolic Dirac operatorsPublication . Ferreira, Milton; Vieira, Nelson Felipe LoureiroIn this paper we study the multidimensional time fractional diffusion-wave equation where the time fractional derivative is in the Caputo sense with order . Applying operational techniques via Fourier and Mellin transforms we obtain an integral representation of the fundamental solution (FS) of the time fractional diffusion-wave operator. Series representations of the FS are explicitly obtained for any dimension. From these we derive the FS for the time fractional parabolic Dirac operator in the form of integral and series representation. Fractional moments of arbitrary order are also computed. To illustrate our results we present and discuss some plots of the FS for some particular values of the dimension and of the fractional parameter.
- Additive manufacturing tooling for the automotive industryPublication . Leal, Rui; Barreiros, F. M.; Alves, L.; Romeiro, F.; Vasco, J. C.; Santos, M.; Marto, C.Automotive industry faces new challenges every day, new design trends and technological deployments from research push companies to develop new models and facelifts in short term, requiring new tools or tool reshaping. Concerning the current world economic scenario, decreasing time for tooling up becomes as important as decreasing time-to-market. Such scenario opens up the horizons for new manufacturing approaches like additive manufacturing, in this case, applied for tooling up a stamping process on the automotive industry for the production of body panels. This approach enables the manufacturing of stamping inserts using similar high performance alloy steel as in conventional tooling, therefore, without losing tool mechanical properties. The stamping tools produced were tested by an automotive company in order to determine tool behaviour under real operating conditions, considering the high level demands of the stamping process. The results obtained enabled to conclude that metal additive manufacturing provided tools for the stamping process with excellent performance with a significant decrease on time-to-tooling.
- Characterization of wireless propagation through traditional Iberian brick wallsPublication . Ferreira, David; Caldeirinha, Rafael F. S.; Fernandes, Telmo R.; Cuinas, InigoThis paper presents the wireless transmission properties for brick walls with different thicknesses and facade finish coatings. The ceramic hollowed bricks under study are traditionally employed in the Iberian residential construction, where the 11, 15 and 20 cm thicknesses are most common in indoor and outdoor walls. For each brick dimension, three different prototypes were manufactured varying in the type of wall finish, i.e.: naked brick, smooth painted plaster and rough painted plaster. The prototypes were measured in an anechoic chamber at frequencies ranging from 680MHz up to 10GHz. Results demonstrate that the brick wall internal heterogeneity, as well as the type of finish, significantly influence the frequency response of the walls.
- Enabling spatial diversity and beamsteering with reduced RF-chains using reconfigurable transmitarraysPublication . João R. Reis; Caldeirinha, Rafael F. S.; Fernandes, Telmo R.; Hammoudeh, AkramThis manuscript introduces a new vision on the implementation of spatial diversity with beamsteering capability, by suppressing the typical beamforming networks of antenna phased arrays and replace them by Reconfigurable Transmitar- rays. Consequently, the radio frequency components, i.e. RF- chains that compose such systems, were replaced by a device with the capability to perform two-dimensional beamsteering relying on single antenna source, hence reducing the number of associated RF hardware in comparison with traditional phased array systems. By spatially distributing side-by-side more than one device, spatial diversity with beamsteering is enabled with an estimated reduction of 1:8 in the number of associated RF-chains. This new concept clearly demonstrates its merit by directly reducing the implementation costs„ RF-chain components and increasing the energy efficiency, specially in larger systems.
- Correlation between the potency of flavonoids for cytochrome c reduction and inhibition of cardiolipin-induced peroxidase activityPublication . Lagoa, Ricardo; Alejandro K. Samhan‐Arias; Carlos Gutierrez‐MerinoThere are large differences between flavonoids to protect against apoptosis, a process in which cytochrome c (Cyt c) plays a key role. In this work, we show that 7 of 13 flavonoids studied have a capacity to reduce Cyt c similar or higher than ascorbate, the flavonols quercetin, kaempferol and myricetin, flavanol epigallocatechin-gallate, anthocyanidins cyanidin and malvidin, and the flavone luteolin. In contrast, the kaempferol 3(O)- and 3,40(O)-methylated forms, the flavanone naringenin, and also apigenin and chrysin, had a negligible reducing capacity. Equilibrium dialysis and quenching of 1,6-diphenyl-1,3,5-hexatriene fluorescence experiments showed that flavonoids did not interfere with Cyt c binding to cardiolipin (CL)/phosphatidylcholine (PC) vesicles. However, the CL-induced loss of Cyt c Soret band intensity was largely attenuated by flavonoids, pointing out a stabilizing action against Cyt c unfolding in the complex. Moreover, flavonoids that behave as Cyt c reductants also inhibited the pro-apoptotic CL-induced peroxidase activity of Cyt c, indicating that modulation of Cyt c signaling are probable mechanisms behind the protective biological activities of flavonoids.
- Intelligent tutorial system based on personalized system of instruction to teach or remind mathematical conceptsPublication . Paiva, R. C.; Ferreira, M. S.; Frade, M. M.The growth of the higher education population and different school paths to access an academic degree has increased the heterogeneity of students inside the classroom. Consequently, the effectiveness of traditional teaching methods has reduced. This paper describes the design, development, implementation and evaluation of a tutoring system (TS) to improve student's engagement in higher mathematics. The TS design was based on the Personalized System of Instruction of the Mastery Learning pedagogical approach and can be implemented in any higher education course with mathematics needs. The TS consists on small self‐paced modularized units of educational contents, including tutorial videos, notes and formative e‐assessment with personalized feedback. The TS ensures that the student is only allowed to proceed to the next unit after he or she achieves the required mastery criterion of the current unit. The TS was implemented in the Quantitative Methods course of an undergraduate degree and received good acceptance from students. It was also recognized that TS contributed to learning and engagement with the discipline. Through an experimental research experience, it has been shown that the imposition of restrictions on the advance to the next level by a mastery criterion leads to a significant improvement in student's engagement and performance.
- Trends on empty exception handlers for Java open source librariesPublication . Nogueira, Ana Filipa; Ribeiro, José; Zenha-Rela, Mario A.Exception-handling structures provide a means to recover from unexpected or undesired flows that occur during software execution, allowing the developer to put the program in a valid state. Still, the application of proper exception-handling strategies is at the bottom of priorities for a great number of developers. Studies have already discussed this subject pinpointing that, frequently, the implementation of exception-handling mechanisms is enforced by compilers. As a consequence, several anti-patterns about Exception-handling are already identified in literature. In this study, we have picked several releases from different Java programs and we investigated one of the most well-known anti-patterns: the empty catch handlers. We have analysed how the empty handlers evolved through several releases of a software product. We have observed some common approaches in terms of empty catches’ evolution. For instance, often an empty catch is transformed into a empty catch with a comment. Moreover, for the majority of the programs, the percentage of empty handlers has decreased when comparing the first and last releases. Future work includes the automation of the analysis allowing the inclusion of data collected from other software artefacts: test suites and data from issue tracking systems.
- Reproductive strategy evaluation of mussel Mytilus galloprovincialis produced in longlines in two areas of Algarve coastPublication . Ramos, Ana Margarete Batista Matias; Joaquim , Sandra Maria DuarteNos últimos anos, a criação de zonas de produção aquícola na costa portuguesa, tem permitido a implementação de empresas offshore para a produção de mexilhão (Mytilus galloprovincialis) sobretudo na costa Algarvia, nomeadamente em Sagres, Lagos e Olhão. O conhecimento da performance reprodutiva das espécies de mexilhão, para além de permitir efetuar uma caracterização biológica, é também essencial para permitir a maximização da produção aquícola, a gestão da fixação de pós-larvas, bem como a gestão da colocação do produto no mercado. Assim, este estudo visa avaliar o ciclo reprodutivo de M. galloprovincialis produzido em duas áreas offshore na costa Algarvia, Olhão e Lagos, através do estudo histológico do desenvolvimento gonadal, composição bioquímica (proteínas, glicogénio e lípidos totais) e índice de condição, durante o período de 19 meses, de março de 2014 a setembro de 2015. Para além destes parâmetros, também foram monitorizados a temperatura da água e a clorofila a para avaliar o efeito do ambiente no ciclo reprodutivo. A atividade reprodutiva dos mexilhões provenientes dos dois locais não segue um ciclo sazonal. O início da gametogénese parece ocorrer durante janeiro/fevereiro para uma pequena percentagem de mexilhões. Ambas as populações apresentaram maior esforço reprodutivo no final da primavera de 2014, onde foi observada a maior percentagem de indivíduos maduros. Não foi observado um período específico de desova, os mexilhões desovaram durante todos meses de amostragem, no entanto o período de desova mais intensa foi observado durante o verão. Os mexilhões estiveram sucessiva e continuamente em recuperação gonadal e em desova durante quase todo o período de estudo. Os valores do índice de condição atingidos foram muito mais baixos em 2015 comparativamente com os do mesmo período de 2014, uma vez que os mexilhões não atingiram o mesmo esforço reprodutivo como em 2014. O ciclo reprodutivo de M. galloprovincialis produzidos nestes dois locais da costa algarvia sofreu uma variabilidade de ano para ano durante o período experimental, onde revelaram uma condição significativamente melhor em 2014 do que em 2015. É amplamente aceite que essas diferenças podem ser correlacionadas com mudanças nas condições ambientais, no entanto, neste estudo, a temperatura e a clorofila a não permitiram explicá-las. Os resultados de ambos os ciclos de armazenamento e utilização de nutrientes mostraram que as populações seguem uma estratégia conservativa, que lhes permite uma rápida recuperação gonadal após a desova, muito provavelmente devido à constante disponibilidade de alimento nos dois locais. O conhecimento alcançado neste estudo pode ser um importante contributo para a rentabilização das empresas, uma vez que estas informações irão permitir uma melhor gestão da produção