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Publications

2016

Influence of different mechanical stimuli in a multi-scale mechanobiological isotropic model for bone remodelling

Authors
Mercuri, EGF; Daniel, AL; Hecke, MB; Carvalho, L;

Publication
MEDICAL ENGINEERING & PHYSICS

Abstract
This work represents a study of a mathematical model that describes the biological response to different mechanical stimuli in a cellular dynamics model for bone remodelling. The biological system discussed herein consists of three specialised cellular types, responsive osteoblasts, active osteoblasts and osteoclasts, three types of signalling molecules, transforming growth factor beta (TGF-beta), receptor activator of nuclear factor kappa-b ligand (RANKL) and osteoprotegerin (OPG) and the parathyroid hormone (PTH). Three proposals for mechanical stimuli were tested: strain energy density (SED), hydrostatic and deviatoric parts of SED. The model was tested in a two-dimensional geometry of a standard human femur. The spatial discretization was performed by the finite element method while the temporal evolution of the variables was calculated by the 4th order Runge-Kutta method. The obtained results represent the temporal evolution of the apparent density distribution and the mean apparent density and thickness for the cortical bone after 600 days of remodelling simulation. The main contributions of this paper are the coupling of mechanical and biological models and the exploration of how the different mechanical stimuli affect the cellular activity in different types of physical activities. The results revealed that hydrostatic SED stimulus was able to form more cortical bone than deviatoric SED and total SED stimuli. The computational model confirms how different mechanical stimuli can impact in the balance of bone homeostasis.

2016

Dipole Antenna for Underwater Radio Communications

Authors
Inacio, SI; Pereira, MR; Santos, HM; Pessoa, LM; Teixeira, FB; Lopes, MJ; Aboderin, O; Salgado, HM;

Publication
2016 IEEE THIRD UNDERWATER COMMUNICATIONS AND NETWORKING CONFERENCE (UCOMMS)

Abstract
The radiation characteristics of a dipole antenna when immersed in both fresh and seawater are assessed through simulation and experimental work. Simulations show that the antenna's bandwidth and radiation pattern change with the properties of the medium where it is placed, namely the conductivity of the medium. Two dipoles antennas with current baluns were built and tested experimentally in freshwater. The tests included the measurement of the insertion loss between two identical dipole antennas and their radiation pattern. The results obtained show a good agreement between the simulation and experimental results.

2016

Situating Case Studies Within the Design Science Research Paradigm: An Instantiation for Collaborative Networks

Authors
Costa, E; Soares, AL; de Sousa, JP;

Publication
COLLABORATION IN A HYPERCONNECTED WORLD

Abstract
A rigorous evaluation of an artifact is one of the fundamental aspects to be considered in Design Science Research projects. This evaluation part becomes even more difficult when a large variety of artifacts must be designed for a project. This can be a challenge for the field of Collaborative Networks, which involves knowledge from several scientific disciplines. Case studies are one of the evaluation methods in Design Science Research that are used for an ex-post evaluation of artifacts. However, we argue that this method can also be used for the ex-ante evaluation, mainly when multidisciplinary research is being carried out. Therefore, the main objective of this paper is to present and discuss a multidisciplinary project of Collaborative Networks using case studies before and after the design of the artifacts. On top of the Design Science Research guidelines, this research is supported by knowledge from Business and Management Studies on how to effectively design and perform Case Study Research for artifact evaluation.

2016

Relation Between Game Genres and Competences for In-Game Certification

Authors
Baptista, R; Coelho, A; de Carvalho, CV;

Publication
SERIOUS GAMES, INTERACTION, AND SIMULATION, SGAMES 2015

Abstract
Digital Games can be effective as learning tools, in applications that can be designated as Serious Games (SG), Games for Learning (GL) or Games-based learning (GBL). SG provide challenges in accordance with the intended learning objectives and can adapt and/or repeat (by allowing error recovering) them according to the learner's level. In training, this aspect is decisive in the acquisition of knowledge, experience and professional skills. The effectiveness of games-based training is directly related to the success on how the challenges promote the acquisition of skills, for which there is no optimal design methodology. This paper presents how a study that identifies the most appropriate game genres to develop specific skills and competences can be used to provide initial solutions to serious games design methodologies. The Triadic Certification model combines the competences defined for each training plan with the challenges designed for the serious games on a matrix that matches the needs and levels.

2016

Influence of low contents of superhydrophilic MWCNT on the properties and cell viability of electrospun poly (butylene adipate-co-terephthalate) fibers

Authors
Rodrigues, BVM; Silva, AS; Melo, GFS; Vasconscellos, LMR; Marciano, FR; Lobo, AO;

Publication
MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS

Abstract
The use of poly (butylene adipate-co-terephthalate) (PBAT) in tissue engineering, more specifically in bone regeneration, has been underexplored to date due to its poor mechanical resistance. In order to overcome this drawback, this investigation presents an approach into the preparation of electrospun nanocomposite fibers from PBAT and low contents of superhydrophilic multi-walled carbon nanotubes (sMWCNT) (0.1-0.5 wt.%) as reinforcing agent. We employed a wide range of characterization techniques to evaluate the properties of the resulting electrospun nanocomposites, including Field Emission Scanning Electronic Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM), tensile tests, contact angle measurements (CA) and biological assays. FE-SEM micrographs showed that while the addition of sMWCNT increased the presence of beads on the electrospun fibers' surfaces, the increase of the neat charge density due to their presence reduced the fibers' average diameter. The tensile test results pointed that sMWCNT acted as reinforcement in the PBAT electrospun matrix, enhancing its tensile strength (from 1.3 to 3.6 MPa with addition of 0.5 wt.% of sMWCNT) and leading to stiffer materials (lower elongation at break). An evaluation using MG63 cells revealed cell attachment into the biomaterials and that all samples were viable for biomedical applications, once no cytotoxic effect was observed. MG-63 cells osteogenic differentiation, measured by ALP activity, showed that mineralized nodules formation was increased in PBAT/0.5%CNTs when compared to control group (cells). This investigation demonstrated a feasible novel approach for producing electrospun nanocomposites from PBAT and sMWCNT with enhanced mechanical properties and adequate cell viability levels, which allows for a wide range of biomedical applications for these materials.

2016

Natural guide-star processing for wide-field laser-assisted AO systems

Authors
Correia, CM; Neichel, B; Conan, JM; Petit, C; Sauvage, JF; Fusco, T; Vernet, JDR; Thatte, N;

Publication
ADAPTIVE OPTICS SYSTEMS V

Abstract
Sky-coverage in laser-Assisted AO observations largely depends on the system's capability to guide on the faintest natural guide-stars possible. Here we give an up-To-date status of our natural guide-star processing tailored to the European-ELT's visible and near-infrared (0.47 to 2.45 µm) integral field spectrograph-Harmoni. We tour the processing of both the isoplanatic and anisoplanatic tilt modes using the spatio-Angular approach whereby the wavefront is estimated directly in the pupil plane avoiding a cumbersome explicit layered estimation on the 35-layer profiles we're currently using. Taking the case of Harmoni, we cover the choice of wave-front sensors, the number and field location of guide-stars, the optimised algorithms to beat down angular anisoplanatism and the performance obtained with different temporal controllers under split high-order/low-order tomography or joint tomography. We consider both atmospheric and far greater telescope wind buffeting disturbances. In addition we provide the sky-coverage estimates thus obtained.

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