Percorrer por autor "Ribeiro, S."
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- Addressing human mobility in Iberian Neolithic and Chalcolithic ditched enclosures: The case of Perdigoes (South Portugal)Publication . Carlos Valera, António; Zalaite, I; Maurer, A. F.; Grimes, V; Silva, A. M.; Ribeiro, S.; Santos, J. F.; Barrocas Dias, C.To access the role of mobility in the social trajectory of Late Neolithic and Chalcolithic societies in the South of Portugal (Southwest Iberia) a project was design to address the human, animal and object/raw material flow present at Perdigoes enclosure. Perdigoes, located in the inner Alentejo region, has a long chronology from Late Middle Neolithic to Late Chalcolithic/Early Bronze Age (middle 4th and 3rd millennium BC). It is a large complex of ditched enclosures (with at least 16 ditches), presenting several funerary contexts, an abundance of faunal remains and significant concentrations of exogenous materials in tombs. In this study human and animal mobility are addressed through Sr-87/Sr-86 isotopic analysis. 69 individuals dating from Late Neolithic and Chalcolithic, with provenance from 9 different archaeological contexts inside the enclosures (tombs, ditches and pits) were analysed. Human data are presented along with previously published strontium isotope ratios from fauna (n = 28; Canis familiaris, Bos taurus, Sus sp., Ovis/Capra, Cervus elaphus, Equus sp.) from the same chronological range and several contextual provenances (Zalaite et al., 2018). Plant samples (n = 20) that cover local and peripheral lithologies were used for establishing local bioavailable strontium isotope ranges. To compare with the Perdigoes results, 9 human samples from 3 megalithic monuments (Cebolinhos 1, Comenda 1 and Vidigueiras 2) of the local settlement network were also analysed. The results show a significant scaled mobility of humans and animals in Perdigoes, a contextual variation between the funerary contexts within the site and a significant contrast with the individuals from local megalithic monuments. These results, combined with other archaeological data at the site, agree with the interpretation of the site as a large aggregation centre integrated in large scale interaction networks.
- Electromechanical actuators based on poly(vinylidene fluoride) with [N-1 (1) (1) (2(OH))][NTf2] and [C(2)mim] [C2SO4]Publication . Dias, J. C.; Martins, Marcos; Ribeiro, S.; Silva, M. M.; Esperança, J. M. S. S.; Ribeiro, C.; Botelho, G.; Costa, C. M.; Lanceros-Mendez, S.Actuators based on electroactive polymers are increasingly used in applications including microelectronic devices and artificial muscles, demanding low voltage operation and controllable switching response. This work reports on the preparation of electroactive actuators based on poly(vinylidene fluoride) (PVDF) composites with 10, 25, and 40 wt% N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl)imide ([N-1 1 1 2(OH)][NTf2]) and 1-Ethyl-3-methylimidazolium Ethylsulfate ([C(2)mim][C2SO4]) ionic liquids (ILs) prepared by solvent casting. Independent of the IL type, its presence leads to the crystallization of PVDF in the piezoelectric beta-phase. The degree of crystallinity and electrical conductivity of the samples strongly depends on ILs type and content. The highest electrical conductivity was found for PVDF/IL composites with 40 wt% of [N-1 1 1 2(OH)][NTf2]. The strain displacement and bending of the PVDF/IL composites were evaluated as a function of IL type and content under applied peak voltages of 2.0, 5.0, and 10.0 V at a frequency of 10 mHz. Strain displacement of the actuators depends more on IL content than on IL type, and the best strain bending response was found for the PVDF/IL composite with 25 wt% of [N-1 1 1 2(OH)][NTf2] at 5.0 V. Further, it is shown that [C(2)mim] [C2SO4]/PVDF composites do not show cytotoxic behavior, being suitable for biomedical applications.