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Browsing by Issue Date, starting with "2020-02"

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  • Validação Exploratória e Confirmatória da Escala de Resiliência Connor-Davidson (CD-RISC-10) numa Amostra de Inscritos em Centros de Emprego
    Publication . Almeida, Maria Helena; Dias, Sara; Xavier, Miguel; Torgal, Jorge
    Introdução: Bonanno definiu resiliência como a capacidade do indivíduo em lidar com os eventos traumáticos, nomeadamente a capacidade de manter os níveis de funcionamento físico e psicológico relativamente estáveis. O objetivo do estudo foi avaliar as propriedades psicométricas da escala de resiliência Connor-Davidson de 10 itens. A escala resumida apresenta boas qualidades psicométricas (α Cronbach – 0,85) quando comparada com a escala longa (25 itens) (α Cronbach – 0,89). Material e Métodos: Obtivemos uma amostra de conveniência de inscritos em centros de emprego que foi aleatoriamente dividida em duas subamostras (amostra 1 = 5127 e amostra 2 = 5134). Aplicámos a análise de componentes principais na amostra 1. Com a amostra 2 procedeu-se à análise fatorial confirmatória usando o método da máxima verosimilhança. Usámos a análise multigrupo para a comparação do modelo fatorial entre os géneros e a situação profissional. Efetuámos a análise convergente e divergente através da análise de correlação de Pearson. Resultados: A análise de componentes principais extraiu um fator com uma variância explicada de 53,97%. A análise fatorial confirmatória comprovou a unidimensionalidade da escala. Confirmámos a invariância entre géneros e situação profissional. A escala de resiliência Connor-Davidson de 10 itens correlacionou-se positivamente com as medidas da escala SF-36 e negativamente com a escala GHQ-12. Discussão: A análise exploratória e confirmatória corroborou a unidimensionalidade e boas propriedades psicométricas, semelhantes à escala original de 10 itens. Conclusão: Trata-se do primeiro estudo de validação desta escala na população portuguesa (Portugal), de acordo com a pesquisa efetuada. Os seus resultados são muito satisfatórios, recomendando-se o seu uso na população portuguesa.
    2020-02Journal article Open access Show more
  • Extruded bioreactor perfusion culture supports the chondrogenic differentiation of human mesenchymal stem/stromal cells in 3D porous poly(ɛ-caprolactone) scaffolds
    Publication . Silva, João C.; Moura, Carla; Borrecho, Gonçalo; Matos, António P. Alves de; Silva, Cláudia L. da; Cabral, Joaquim M. S.; Bártolo, Paulo J.; Linhardt, Robert J.; Ferreira, Frederico Castelo
    Novel bioengineering strategies for the ex vivo fabrication of native-like tissue-engineered cartilage are crucial for the translation of these approaches to clinically manage highly prevalent and debilitating joint diseases. Bioreactors that provide different biophysical stimuli have been used in tissue engineering approaches aimed at enhancing the quality of the cartilage tissue generated. However, such systems are often highly complex, expensive, and not very versatile. In the current study, a novel, cost-effective, and customizable perfusion bioreactor totally fabricated by additive manufacturing (AM) is proposed for the study of the effect of fluid flow on the chondrogenic differentiation of human bone-marrow mesenchymal stem/stromal cells (hBMSCs) in 3D porous poly(ɛ-caprolactone) (PCL) scaffolds. hBMSCs are first seeded and grown on PCL scaffolds and hBMSC–PCL constructs are then transferred to 3D-extruded bioreactors for continuous perfusion culture under chondrogenic inductive conditions. Perfused constructs show similar cell metabolic activity and significantly higher sulfated glycosaminoglycan production (≈1.8-fold) in comparison to their non-perfused counterparts. Importantly, perfusion bioreactor culture significantly promoted the expression of chondrogenic marker genes while downregulating hypertrophy. This work highlights the potential of customizable AM platforms for the development of novel personalized repair strategies and more reliable in vitro models with a wide range of applications.
    2020-02Journal article Restricted access Show more
  • Estimation of prevalence in rare disease using pooled samples
    Publication . Martins, J. P.; Santos, R.; Felgueiras, M.
    The use of pooled samples for screening infected individuals is a known procedure to reduce costs. In an estimation problem, the aim is only to determine how many individuals are infected instead of determining who is infected (classification problem). In that setting, our goal was to compare the performance of using one or two-dimensional arrays. The best performance was established according to one of the following criteria: minimizing the number of individuals or the number of tests required to attain a certain estimate accuracy. It is observed that when we want to minimize the number of individuals used, the two-dimensional procedures have a little advantage over the one-dimensional procedures. However, when the major concern is the cost, the one-dimensional procedures clearly outperform the two-dimensional procedures.
    2020-02Conference paper Open access Show more
  • Preface
    Publication . Dantas, José Guilherme Leitão; Carvalho, Luísa Cagica
    Over the last years we have witnessed the enormous success of quite demanding ventures all over the world. We are particularly talking about technology-based projects which, in some cases, have revolutionized the way we live. Their impact on the national and international level has been unequivocal concerning jobs and wealth creation, the new solutions their development have enabled, etc. That kind of ventures, regardless of their outstanding relevance, is the exception rather than the norm, i.e., they are only the visible tip of the iceberg, in that they only account for a very small percentage of the entrepreneurial activity. Nevertheless, they belong to the so-called mainstream entrepreneurship, are the dream of every economy, and deserve the attention of many researchers. (...) In short, the book starts by covering a set of activities upstream of the entrepreneurial activity, and then addresses a significant, though not exhaustive, set of different types of entrepreneurship, often paving the way for more in-depth investigations which will allow us to continue expanding such a relevant theme for our collective future.
    2020-02Journal editorial Open access Show more
  • Additive manufactured porous biomaterials targeting orthopedic implants: A suitable combination of mechanical, physical and topological properties
    Publication . Bartolomeu, F.; Dourado, N.; Pereira, F.; Alves, N.; Miranda, G.; Silva, F. S.
    Orthopedic implants are under incessant advancement to improve their interactions with surrounding bone tissue aiming to ensure successful outcomes for patients. A successful biological interaction between implant and surrounding bone depends on the combination of mechanical, physical and topological properties. Hence, Ti6Al4V cellular structures appear as very promising solutions towards the improvement of conventional orthopedic implants. This work addresses a set of fundamental tools that allow improving the design of Ti6Al4V cellular structures produced by Selective Laser Melting (SLM). Three-point bending tests were carried out to estimate the elastic modulus of the produced structures. Morphological analysis allowed to evaluate the dimensional differences that were noticed between the model CAD and the SLM structures. Finite element models (adjusted CAD) were constructed with the experimentally obtained dimensions to replicate the mechanical response of the SLM structures. Linear correlations were systematically found for the dimensions of the SLM structures as a function of the designed model CAD dimensions. This has also been observed for the measured porosities as a function of the designed CAD models. This data can be used in further FE analyses as design guidelines to help engineers fabricating near-net-shape SLM Ti6Al4V cellular structures. Besides, polished and sandblasted surface treatments performed on the Ti6Al4V cellular structures allowed to obtain suitable properties regarding roughness and wettability when compared to as-produced surfaces. The capillarity tests showed that all the analyzed Ti6Al4V structures are able to transport fluid along its structure. The cell viability tests demonstrate Ti6Al4V cellular structures SLM produced did not release toxic substances to the medium, indicating that these structures can assure a suitable environment for cells to proliferate and attach. This study proposes a design methodology for Ti6Al4V cellular structures, that owe suitable mechanical properties but also provide a proper combination of porosity, roughness, wettability, capillarity and cell viability, all of them relevant for orthopedic applications. A Ti6Al4V cellular structured hip implant prototype gathering the suitable features addressed in this study was successfully SLM-produced.
    2020-02Journal article Open access Show more
  • Multi-Gigabit/s OFDM real-time based transceiver engine for emerging 5G MIMO systems
    Publication . Ribeiro, Carlos; Gomes, Rodolfo; Duarte, Luís; Hammoudeh, Akram; Caldeirinha, Rafael F. S.
    This paper presents a highly scalable multi-Gigabit/s Real-Time (RT) Wideband (WB) Orthogonal Frequency Division Multiplexing (OFDM) processing chain for 5G applications. It is aimed to significantly reduce the Hardware (HW) footprint of Multiple Input Multiple Output (MIMO) systems. In this context, implementation complexity results for MIMO configurations of 2 × 2, 4 × 4 and 8 × 8, enabled at sampling rates of 245.76, 122.88, 61.44 and 30.72 MHz, respectively, are compared with the ones from conventional MIMO architectures. For example, for a 8 × 8 MIMO–OFDM configuration implementation, savings of up to 87% are achieved when compared with conventional design methods, in terms of DSP48E1 slices. Moreover, in a Xilinx Virtex 7 XC7VX485T, it is shown that a second processing branch might be implemented, leading to a 5 Gbps (using 1024 Quadrature Amplitude Modulation (QAM)) Single-Input Single-Output (SISO) link or a 16 × 16 MIMO configuration. Finally, in order to validate the proposed architecture, the impact of its inclusion on a complete Field Programmable Gate Array (FPGA) 8 × 8 OFDM system, at LTE's highest sampling rate of 30.72 MHz, is evaluated. Subsequently, it is demonstrated that this does not affect the performance of OFDM, even in the presence of Carrier Frequency Offset (CFO).
    2020-02Journal article Open access Show more
  • A resolução por iniciativa do trabalhador
    Publication . Aires, Sara Margarida Simões; Costa, Ana Isabel Lambelho; Girão, Filomena
    O presente relatório visa apresentar o estágio curricular desenvolvido no âmbito do 2.º ano do curso de Mestrado em Solicitadoria de Empresa. O estágio versou na área do Direito do Trabalho e teve como principal objetivo propiciar a aquisição de competências práticas nessa área, como a realização de pareceres jurídicos, contratos de trabalho, petições iniciais, auditorias laborais, entre outras atividades. No primeiro capítulo iremos caracterizar a entidade de acolhimento onde o estágio curricular decorreu e referir as várias atividades desenvolvidas. No segundo capítulo, a partir de uma situação real, abordaremos a resolução por iniciativa do trabalhador baseada na justa causa subjetiva, analisando o procedimento que o trabalhador terá de realizar, a indemnização que terá direito a receber e as causas e consequências da ilicitude da resolução. Tratando-se de um trabalho iminentemente prático, ao longo do capítulo articularemos os fundamentos legais e doutrinais subjacentes à resolução por iniciativa do trabalhador com a componente prática do estudo de caso.
    2020-02-01Master thesis Open access Show more
  • Evaluation of post-earthquake fire capacity of a reinforced concrete one bay plane frame under ISO fire exposure
    Publication . Vitorino, Hugo; Rodrigues, Hugo; Couto, Carlos
    Post-earthquake fires may appear after a large earthquake and its effects on urban areas can be even worse that the effects of the earthquake itself. The aim of the present work is to define a methodology to evaluate the consequences of the damage introduced by the seismic events on the fire resistance of reinforced concrete frames. It was performed several numerical analyses in reinforce concrete frames using the program SAFIR, considering the thermal and mechanical analysis of the structure. The variables in the analysis were the type of damage in the frames and the number of fire frontiers in the columns. The thermal analysis was performed using the standard fire curve ISO 834. The results show that the damage imposed by earthquake on reinforced concrete frames reduces the fire resistance of the frames. The time until collapse of the frames exposed to fire where was considered the most severe damage was about 2 h lower when compared to the frames without damage exposed to fire.
    2020-02-01Journal article Restricted access Show more
  • Comparison of motivational factors between the practice of sports of nature, competitive adventure and leisure
    Publication . Brandão, António; Frontini, Roberta; Peixoto, Diogo; Fernandes, Daniel; Clemente, Filipe Manuel
    The main aim of this study was to compare sports practitioners of a competitive and leisure nature sports regarding their motivations for practice. The sample consisted of 631 adults (504 men and 127 women) who practiced nature and adventure sports. Participants answered an assessment protocol composed of a sociodemographic form and the Exercise Motivation Inventory - 2 (EMI-2) questionnaire. Among leisure and competition practitioners, variations were analyzed using standardized effect size differences (ES) with 90% Confidence Interval (CI). The following scale was used to interpret the magnitude effect: <0,2, trivial; 0,2-0,6, small; 0,6-1,2, moderate; > 1,2, large. The probabilities were tested considering the smallest worthwhile changes (SW, 0,2 x between SD subjects). The following scale was used for qualitative probabilities: 25-75%, possibly; 75-95%, likely; 95-99% very likely; e> 99% almost certain. Differences in variables were tested regarding the following factors: Social Recognition, Positive Health, Weight, Stress Management, Revitalisation, Enjoyment, Challenge, Affiliation, Competition, Health Pressures, Health Avoidance, Appearance, Strength & Endurance and Nimbleness. Only the variables Enjoyment and Competition had moderate magnitude when comparing leisure to competitive practitioners. When comparing within gender, we found that the variable Competition is more noticeable in females compared to leisure having a probability of almost certain with large magnitude on the Enjoyment variable -29.2% [-36.8;-20.6]; ES: -2.17 [-2.89;-1.45] and competition -50.7% [-60.6;-38.4]; ES: -1.52 [-2.00;-1.04]. Understanding the motives that fit the practice of a particular sport is essential to tailor a strategy and make sports plans more appealing and interesting for their practitioners. The Enjoyment and Competition factors were the most significant, which influenced the gender differences between and when comparing the profile of leisure and competitors.
    2020-02-05Journal article Open access Show more
  • The impact of transformational leadership on employees’ affective commitment, stress and performance
    Publication . Ribeiro, Neuza; Gomes, Daniel Roque; Duarte, Ana Patrícia; Semedo, Suzete; Medina, Inês
    2020-02-06Conference object Restricted access Show more