Elastic properties of carbon nanotubes and their heterojunctions

Comprehensive studies on the modelling and numerical simulation of the mechanical behaviour under tension, bending and torsion of single-walled carbon nanotubes and their heterojunctions are performed. It is proposed to deduce the mechanical properties of the carbon nanotubes heterojunctions from the knowledge of the mechanical properties of the single-walled carbon nanotubes, which are their constituent key unit

Pressões antropogénicas nas bacias hidrográficas dos Rios Sôrdo, Pinhão e Ribeira de Vila Chã : causas, consequências e respostas

A área estudada situa-se nas bacias hidrográficas dos rios Sôrdo, Pinhão e Ribeira de Vila Chã, abrangendo estes três rios e seus afluentes, no sentido de estudar todo o tipo de pressões antropogénicas exercidas ao longo destas bacias. Este trabalho compreende a revisão bibliográfica e descrição detalhada das ferramentas a utilizar no desenvolvimento de uma metodologia, que, abordará sequencialmente, as seguintes etapas: levantamento e tipificação de todo o tipo de pressões exercidas ao longo das bacias da área de estudo, descrição da elaboração de matrizes estruturais, explicação do tratamento estatístico multivariado a utilizar para tratamento destes dados, utilizando o programa STELLA, definição da produção de uma base de dados a partir destes elementos em SIG (Sistemas de Informação Geográficos). Ao longo desta apresentação será delineado um esquema metodológico onde serão tipificados os diferentes tipos de pressões exercidas nas várias bacias, relacionando as tipificações entre si de modo a criar um modelo de correlação entre a tipificação utilizada e as consequências destas pressões nas bacias. Será descrito o modelo a criar de gestão dinâmica de toda a área de estudo

Detection of new eruptions in the Magellanic Clouds LBVs R 40 and R 110

We performed a spectroscopic and photometric analysis to study new eruptions in two luminous blue variables (LBVs) in the Magellanic Clouds. We detected a strong new eruption in the LBV R40 that reached $V \sim 9.2$ in 2016, which is around $1.3$ mag brighter than the minimum registered in 1985. During this new eruption, the star changed from an A-type to a late F-type spectrum. Based on photometric and spectroscopic empirical calibrations and synthetic spectral modeling, we determine that R\,40 reached $T_{\mathrm{eff}} = 5800-6300$~K during this new eruption. This object is thereby probably one of the coolest identified LBVs. We could also identify an enrichment of nitrogen and r- and s-process elements. We detected a weak eruption in the LBV R 110 with a maximum of $V \sim 9.9$ mag in 2011, that is, around $1.0$ mag brighter than in the quiescent phase. On the other hand, this new eruption is about $0.2$ mag fainter than the first eruption detected in 1990, but the temperature did not decrease below 8500 K. Spitzer spectra show indications of cool dust in the circumstellar environment of both stars, but no hot or warm dust was present, except by the probable presence of PAHs in R\,110. We also discuss a possible post-red supergiant nature for both stars

Effect of high hydrostatic pressure on the quality of four edible flowers: Viola × wittrockiana, Centaurea cyanus, Borago officinalis and Camellia japonica

The aim of the study was to evaluate the effect of high hydrostatic pressure (HHP) on the appearance, bioactivity and microbial content of four edible flowers along storage. Several treatments at 75–450 MPa and holding times (1, 5 and 10 min) were applied. Borage and camellia were unacceptable after all treatments, while centaurea showed good appearance at 100/5 MPa min -1 ; however, the shelf life did not increase. Pansies treated at 75/5 and 75/10 MPa min -1 also retained the appearance of fresh flowers. Furthermore, pansies submitted at 75/5 MPa min -1 maintained good appearance over 20 days of storage at 4 °C, while the untreated remained satisfactory only until 6 days. Even though no significant differences on microbial load were observed between untreated and HHP-treated pansies in day 0, HHP induced the production of bioactive compounds, increasing the shelf life of pansies. So, the HHP treatment is a promising technology for Viola × wittrockiana.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT, Portugal) for the financial support provided by the research grant (SFRH/BD/95853/2013), QOPNA Research Unit (FCT UID/QUI/00062/2013), REQUIMTE (PEst/UID/QUI/50006/2013) and ‘Project (NORTE-07-0124- FEDER-000069)’, and CIMO (UID/AGR/00690/2013), through national funds and when applicable cofinanced by the FEDER, within the PT2020 Partnership Agreement.info:eu-repo/semantics/publishedVersio

Ultra-low-cycle fatigue of pipeline steels

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002.Pipelines and piping components when subjected to extreme loading conditions (e.g. earthquakes, hurricanes, support settlements, industrial plant shutdown) undergo large plastic deformations, associated with widespread yielding, leading to fracture, either due to monotonic loading or ultra-low-cycle fatigue (ULCF). ULCF is neither satisfactorily understood nor conveniently investigated compared to the monotonic ductile or low-cycle fatigue damage mechanisms. Having in mind the existing gaps in the knowledge about the ULCF, the ULCF European project, coordinated by FEUP, aimed at developing innovative computational methodologies for the simulation of steel material fracture under both monotonic and ultra-low-cycle fatigue, based on a significant experimental program including small and large-scale tests. This presentation makes an overview of the main results of the project, which includes: i) Database of small-scale testing data covering the X52, X60, X65, X70 and X80 piping steel grades. Smooth and special notched specimens were tested under both monotonic and cyclic (LCF & ULCF) loading. Dedicated monotonic tests were performed to assess the anisotropic behaviour of some materials (X70/X80). Combined multiaxial loading conditions were also investigated. ii) Database of full-scale testing results covering same materials also tested under small-scale conditions was generated. Monotonic and ULCF tests of pipe components were performed. ULCF tests included buckled and dented pipes, elbows and straight pipes. iii) New constitutive models for both monotonic and ULCF loading were proposed. Besides the Barcelona model, alternative approaches were investigated. Further constitutive refinements of nonlinear monotonic damage and enhanced anisotropic models, were also studied. iv) Developed constitutive models were calibrated and validated using experimentally derived testing data

Freezing of edible flowers: Effect on microbial and antioxidant quality during storage

Edible flowers are a new gourmet product; however, they are not always available all years. Thus, it is essential to find out technologies to guarantee this product for a longer time. Flowers of four species (borage [Borago officinalis], heartsease [Viola tricolor], kalanchoe [Kalanchoe blossfeldiana], and dandelion [Taraxacum officinale]) were subjected to freezing (in their natural form and in ice cubes) and analyzed in terms of visual appearance, the content of flavonoids, hydrolysable tannins, phenolics, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and reducing power), and microbial quality after storage for 1 and 3 months. Flowers in ice cubes showed similar appearance to fresh ones during the 3 months of storage, whereas frozen flowers were only equivalent up to 1 month with the exception of kalanchoe. Even though flowers in ice cubes showed good appearance after 3 months of storage, they had the lowest values of bioactive compounds and antioxidant activity. On the contrary, when frozen, the content of bioactive compounds maintained or even increased up to 1 month of storage compared to fresh flowers, except for borage. Furthermore, in both freezing treatments, the microorganisms’ counts decreased or maintained when compared to fresh samples, except in dandelion. In general, both treatments may allow keeping the flowers after their flowering times.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT, Portugal) for the financial support provided by the research grant SFRH/BD/95853/2013 to Luana Fernandes and FCT/MCT for the financial support to QOPNA Research Unit (FCT UID/QUI/00062/2019) and LAQV Research Unit (UID/QUI/50006/2019) through national funds and cofinanced by the FEDER within the PT2020 Partnership Agreement. Furthermore, the authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2019).info:eu-repo/semantics/publishedVersio

Physicochemical, antioxidant and microbial properties of crystallized pansies (Viola × wittrockiana) during storage

Edible flowers, such as pansies, have a short shelf-life. Crystallization is a treatment used to prolong the shelflife of fruits and vegetables. So, the aim of the present work was to investigate the effect of crystallization in the physicochemical, microbial and antioxidant properties of pansies (Viola wittrockiana) during room temperature storage (7, 15, 30, 60 and 90 days). Comparing fresh and crystallized pansies, significant differences were detected. After 90 days of storage, crystallized pansies kept similar appearance to those immediately after treatment. A significant decrease in water activity, moisture, ash and protein contents was observed between 0 and 90 days of storage for crystallized pansies. Some bioactive compounds, such as flavonoids and monomeric anthocyanins, showed a significant decrease after 90 days of storage, while hydrolysable tannins increased. Concerning phenolic compounds, these maintained constant along storage. The microbial load of crystallized pansies during all storage time was lower than fresh ones. So, crystallization can be an effective method for pansies preservation, being some nutritional and bioactive compounds, little affected during storage. However, crystallization contributed to a high increase in sugar content and energy values compared to fresh pansies.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors acknowledge the Portuguese Foundation for Science and Technology (FCT, Portugal) for the financial support provided by the research grant (SFRH/BD/95853/2013), QOPNA research Unit (FCT UID/QUI/00062/2013), REQUIMTE (PEst/UID/QUI/50006/2013) and ‘Project [NORTE-07-0124-FEDER-000069]’ and CIMO (UID/AGR/00690/2013), through national funds and when applicable co-financed by the FEDER, within the PT2020 Partnership Agreement.info:eu-repo/semantics/publishedVersio