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- Möbius gyrogroups: a Clifford algebra approachPublication . Ferreira, Milton; Ren, G.Using the Clifford algebra formalism we study the Möbius gyrogroup of the ball of radius t of the paravector space, where V is a finite-dimensional real vector space. We characterize all the gyro-subgroups of the Möbius gyrogroup and we construct left and right factorizations with respect to an arbitrary gyro-subgroup for the paravector ball. The geometric and algebraic properties of the equivalence classes are investigated. We show that the equivalence classes locate in a k-dimensional sphere, where k is the dimension of the gyro-subgroup, and the resulting quotient spaces are again Möbius gyrogroups. With the algebraic structure of the factorizations, we study the sections of Möbius fiber bundles inherited by the Möbius projectors.
- Numerical modelling of the Young’s modulus of syntactic foamsPublication . Antunes, F.V.; Ferreira, J.A.M.; Capela, C.Syntactic foams are particulate composites obtained by filling a polymeric matrix with hollow solid inclusions. Numerical simulations are an important tool to predict material behaviour and optimize the mechanical properties. The aim of this work is to develop a multi-phase numerical model to predict stiffness of the syntactic foams. The numerical parameters were identified and optimized, and the numerical predictions were validated with experimental results from 3-point bending tests. Different physical parameters were then studied, namely the volume fraction and the size of the filler, the elastic properties of filler and matrix and the inclusion's thickness. A sensitivity analysis was developed to quantify the importance of these different parameters, and the rigidity of the matrix was found to be the most influent. The parametric space was scanned and a numerical interpolation procedure implemented based on shape functions of finite element method. The procedure is an interesting tool for design and was used to identify the particles having stiffness equal to the matrix.
- Cogeneration supply by bio-energy for a sustainable hotel building management systemPublication . Galvão, João Rafael; Leitão, Sérgio Augusto; Silva, Salvador Malheiro; Gaio, Tiago ManuelIn this work we presented the development of an energy model based on a mixed system of renewable energy, with primary energy sources as solar and biomass. It is a hybrid and autonomous system with solar PV panels and gasification cogeneration technology. Also it is an environment friendly process aiming the reduction of energy demand, costs and emissions. This energy model is a new sustainable standard about energy consumption efficiency (electrical and thermal demands) of a small hotel building and a relevant contribution to certify the building, in compliance with the laws of the country on the thermal performance of buildings.
- What factors of satisfaction and motivation are affecting the development of the academic career in Portuguese higher education institutions?Publication . Machado-Taylor, Maria de Lourdes; Soares, Virgílio Meira; Ferreira, Jose; Gouveia, Odília Maria RochaAn important constituent group and a key resource of higher education institutions (HEIs) is the faculty or academic staff. The centrality of the faculty role makes it a primary sculptor of institutional culture and has implications for the quality of the institution and therefore has a major role in achieving the objectives of the institution. Demand for academic staff in higher education has been increasing and may be expected to continue to increase. Moreover the performance of academic staff as teachers and researchers determines much of the student satisfaction and has an impact on student learning. There are many factors that serve to undermine the commitment of academics to their institutions and careers. Job satisfaction is important in revitalizing staff motivation and in keeping their enthusiasm alive. Well motivated academic staff can, with appropriate support, build a national and international reputation for themselves and the institution in the professional areas, in research and in publishing. This paper aims to identify the issues and their impacts on academic staff job satisfaction and motivation within Portuguese higher education institutions reporting an ongoing study financed by the European Union through the Portuguese Foundation for Science and Technology.
- Biomimetic composite coating on rapid prototyped scaffolds for bone tissue engineeringPublication . Arafat, M. Tarik; Lam, Christopher X.F.; Ekaputra, Andrew K.; Wong, Siew Yee; Li, Xu; Gibson, IanThe objective of this present study was to improve the functional performance of rapid prototyped scaffolds for bone tissue engineering through biomimetic composite coating. Rapid prototyped poly(ε-caprolactone)/tri-calcium phosphate (PCL/TCP) scaffolds were fabricated using the screw extrusion system (SES). The fabricated PCL/TCP scaffolds were coated with a carbonated hydroxyapatite (CHA)-gelatin composite via biomimetic co-precipitation. The structure of the prepared CHA-gelatin composite coating was studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Compressive mechanical testing revealed that the coating process did not have any detrimental effect on the mechanical properties of the scaffolds. The cell-scaffold interaction was studied by culturing porcine bone marrow stromal cells (BMSCs) on the scaffolds and assessing the proliferation and bone-related gene and protein expression capabilities of the cells. Confocal laser microscopy and SEM images of the cell-scaffold constructs showed a uniformly distributed cell sheet and accumulation of extracellular matrix in the interior of CHA-gelatin composite-coated PCL/TCP scaffolds. The proliferation rate of BMSCs on CHA-gelatin composite-coated PCL/TCP scaffolds was about 2.3 and 1.7 times higher than that on PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds, respectively, by day 10. Furthermore, reverse transcription polymerase chain reaction and Western blot analysis revealed that CHA-gelatin composite-coated PCL/TCP scaffolds stimulate osteogenic differentiation of BMSCs the most, compared with PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds. These results demonstrate that CHA-gelatin composite-coated rapid prototyped PCL/TCP scaffolds are promising for bone tissue engineering.
- The effects of the nitrofuran furaltadone on Ulva lactucaPublication . Leston, Sara; Nunes, Margarida; Viegas, Ivan; Lemos, Marco F. L.; Freitas, Andreia; Barbosa, Jorge; Ramos, Fernando; Pardal, Miguel A.The use of pharmaceuticals in the food production industry as prophylatic and therapeutic agents is necessary to promote animal health, but may entail significant consequences to natural ecosystems, especially in the cases of overdosing and use of banned pharmaceuticals. The vast effects that antibiotics released into the environment have on non-target organisms are already under the scope of researchers but little attention has been given to primary producers such as macroalgae. The present study assessed furaltadone's, an antibacterial agent illegally used for veterinary purposes, uptake capacity by Ulva lactuca and its effect in the growth of this cosmopolitan macroalgae. Differences in macroalgal growth were shown when submitted to prophylactic and therapeutic concentrations of furaltadone in the water (16 and 32μgmL-1, respectively). The therapeutic concentration caused higher growth impairment than the prophylactic treatment did, with 87.5% and 58% reductions respectively. Furthermore, together with data collected from the accumulation assays, with values of internal concentrations as high as 18.84μgg-1 WW, suggest that the macroalgae U. lactuca should be included in field surveys as a biomonitor for the detection of nitrofurans.
- Effect of shoulder cavity and welding parameters on friction stir welding of thin copper sheetsPublication . Leal, R. M.; Sakharova, N.; Vilaça, P.; Rodrigues, D. M.; Loureiro, A.The aim of this investigation was to study the influence of shoulder cavity and welding parameters on torque, defect formation, microstructure and mechanical properties of friction stir welds in very thin sheets of deoxidised copper. Three types of tools were used: a flat shoulder tool and two tools with conical shoulder cavities of 3 and 6° respectively. The welding parameters analysed were tool rotation and traverse speeds. It was observed that the torque, the microstructure and hardness and the formation of defects in the welds are influenced mainly by tool rotation speed and, to a lesser extent, by the traverse speed and shoulder cavity. The tensile properties of welds carried out at high rotation speeds are little affected by the shoulder cavity.
- Optimization in the immobilization of penicillin G acylase by entrapment in xerogel particles with magnetic propertiesPublication . Bernardino, Susana; Estrela, Nídia; Ochoa-Mendes, Vanessa; Fernandes, Pedro; Fonseca, Luís P.Biocatalysis presents a sound alternative to chemical synthesis in the field of drug production, given the highly selective nature of biological catalysts. Penicillin G Acylase (PGA) from E. coli is currently used to hydrolyze penicillin G (PG) and catalyzes the synthesis of β-lactam antibiotics. In this work, particular emphasis is given to recent developments in penicillin G acylase immobilization, by entrapment simultaneously with nano-magnetic particles in a silica matrix. The sol-gel biocatalytic particles were prepared either by a conventional method (crushed powder) or by a more recent approach, based in an emulsion system using 150 mM AOT/isooctane, which allowed for the formation of spherical micro- and nanobeads. The effects on PGA activity of different sol-gel precursors, additives, enzyme concentration, aging, drying conditions and mechanical stability were evaluated. After these optimization studies, a mechanically stable carrier based on porous xerogels silica matrixes, starting from tetramethoxysilane (TMOS) with 65-67% PGA activity yield in these carriers allowed an immobilization yield of 74 mg protein g dry sol-gel -1 and 930 Ug dry sol-gel -1 for specific activity were obtained.