Browsing by Issue Date, starting with "2020-07"
Now showing 1 - 10 of 104
Results Per Page
Sort Options
- A three-dimensional approach for contact detection between realistic wheel and rail surfaces for improved railway dynamic analysisPublication . Marques, Filipe; Magalhães, Hugo; Pombo, João; Ambrosio, Jorge; Flores, PauloThe wheel-rail contact modeling problem assumes a preponderant role on the dynamic analysis of railway systems using multibody systems formulations. The accurate and efficient evaluation of both location and magnitude of the wheel-rail contact forces is fundamental for the development of reliable computational tools. The wheel concave zone might be a source of numerical difficulties when searching the contact points, which has been neglected in several works. Here, it is demonstrated that the minimum distance method does not always converge when the wheel surface is not fully convex, being an alternative methodology proposed to perform the contact detection. This approach examines independently the contact between each wheel strip and the rail, where the maximum virtual penetration is determined and associated with the location of the contact point. Then, an Hertzian-based force model is considered for both normal and tangential forces. The results obtained from dynamic simulations show that the minimum distance method and the proposed methodology provide a similar response for simplified wheel profiles. However, the new approach described here is reliable in the identification of the contact point when realistic wheel profiles are considered, which is not the case with the minimum distance method.
- Personal protective equipment used as sampling methods to assess exposure to bioburden: an added value to be considered?Publication . Viegas, Carla; Dias, Marta; Almeida, Beatriz; Carolino, ElisabetePersonal protective equipment, such as mechanical protection gloves, is of compulsory use in the Portuguese waste sorting industry. This study intends to assess the bioburden present in this protection equipment and discuss the possibility to be considered as a potential passive sampling method to assess occupational exposure to microbial contamination. The bacterial contamination in the glove samples ranged from 0 CFU.m-2 to uncountable, and the gram-negative bacteria contamination from 2x103 CFU.m-2 to uncountable. Sorting waste and feeding machines with waste (FMW) were the two workstations where gloves presented a higher prevalence of Gram- bacteria. The fungal contamination in the gloves samples ranged from 0 CFU.m-2 to uncountable. The FMW workstation presented the highest bacterial and fungal concentrations. Concerning the gloves wearing time, only a significant, positive, and weak-intensity correlation was detected with the fungal counts on MEA (r = 0.291, p = 0.022). Protection gloves can be used as passive sampling methods to assess occupational exposure to bioburden in the waste-sorting industry. Furthermore, the obtained results can be used to prioritize occupational health interventions and for training and education programs held to workers.
- Studying the impact of different body positioning, squatting, and unipodal flexion on perfusion in the lower limb: an exploratory approach complemented with optical spectroscopy (TiVi)Publication . Nuno, Sérgio; Florindo, Margarida; Silva, Henrique; Rodrigues, Luis MonteiroBody posture and movement seem to be responsible for multiple variations of microcirculation in the foot, although difficulties associated with measurement during movement have limited their characterization. This pilot study sought to explore a new non-invasive instrument based on polarized light spectroscopy – the TiVi system, under orthostatic and dynamic conditions. Five healthy participants (duly informed, 26.0 ± 6.5 years of age) of both genders were selected. The protocol involved sequential posture changes (orthostatic variation) and dynamic movements (squatting and unipodal flexion). Perfusion variations were evaluated in both feet by laser-Doppler flowmetry (LDF) and polarized spectroscopy (TiVi). Both systems revealed the same type of modification of these flow-related variables. The most pronounced changes were obtained with exercise, especially with squatting, which caused a marked increase in foot perfusion. Less dramatic but in the same direction, the increased perfusion with unipodal flexion was also observed in the contralateral limb. This study confirmed the interest in using the TiVi system in these domains, as well as the appropriateness of this experimental design to look deeper into the impact of lower limb movement on the functional dynamics of the foot.
- Sustainability of European agricultural holdingsPublication . Dos Santos, Maria José Palma Lampreia; Ahmad, NawazEuropean agricultural activity has an important contribution to European and global food security and also in the preservation of countryside and livelihood. The main goal of this paper is to analyze the agricultural sustainability of the twenty-eight Member States of the European Union in order to promote sustainable agriculture, food security and rural development in the European region. Information and data used are obtained from the European Commission database. The methodology includes the min–max approach and multivariate techniques, namely, Cluster and Factorial Analysis. The findings show the existence of three different clusters of farms in European countries, namely, Central European countries, New Eastern Member States, and the Mediterranean countries. The results also conclude that European agriculture and their respective farms have moderate sustainability where the subsidies from Common Agricultural Policy have a positive impact on. Moreover, agricultural activity in the European Central countries presents the highest value in economic contribution, whereas the Mediterranean countries present more contribution in environmental terms. The highest contribution in terms of creating rural jobs is found in Eastern countries. The main conclusion highlights the need to better adjust agricultural policies among the European Member States in order to better promote the sustainability of agriculture in Europe.
- Personal protective equipment used as sampling methods to assess exposure to bioburden: an added value to be considered?Publication . Viegas, Carla; Dias, Marta; Almeida, Beatriz; Carolino, ElisabeteWaste from non-biodegradable materials is sorted in waste sorting units to produce dry recyclables raw materials, leading to direct access and exposure of workers to waste and its contaminants. The organic residues present in waste serve as a substrate for numerous microorganisms, increasing workers’ exposure to microbial contaminants, with previous studies associating health risks with these environments. In Portugal, mechanical protection gloves (MPG) are of mandatory use. During their use, sweat is released, and, consequently, the humidity of the material increases. Additionally, the temperature inside the glove leads to conditions favorable to the growth of microorganisms. This study intends to assess the bioburden present in MPG and discuss the possibility to be considered as potential passive sampling methods to assess occupational exposure to microbial contamination.
- Determinants of the Portuguese government bond yieldsPublication . Barradas, Ricardo; Pinho, AndréThis paper conducts an empirical examination of the determinants of the 10‐, 5‐ and 1‐year Portuguese government bond yields by performing a time series econometric analysis for the period between the first quarter of 2000 and the last quarter of 2016. The literature suggests that the evolution of government bond yields depends on three main risk drivers, namely credit risk, global risk aversion and liquidity risk. We estimate three equations for the 10‐, 5‐ and 1‐year Portuguese government bond yields, including eight independent variables (macroeconomic performance, fiscal conditions, foreign borrowing, the inflation rate, labour productivity, the demographic situation, global risk aversion and liquidity risk) to take into account all three risk drivers referred to in the literature. Our results show that there are no significant differences in the determinants of the Portuguese government bond yields among the different maturities, either in the long term or in the short term. Our results also confirm that all three of the risk drivers have exerted a strong influence on the evolution of the Portuguese government bond yields. Liquidity risk, foreign borrowing and the inflation rate are the main triggers of the rise in the Portuguese government bond yields, which does not counterweigh the beneficial effects played by the fiscal conditions, labour productivity and demographic situation.
- Impact of OVL variation on AUC bias estimated by non-parametric methodsPublication . Silva, Carina; Turkman, Maria Antónia Amaral; Sousa, LiseteThe area under the ROC curve (AUC) is the most commonly used index in the ROC methodology to evaluate the performance of a classifier that discriminates between two mutually exclusive conditions. The AUC can admit values between 0.5 and 1, where values close to 1 indicate that the model of classification has high discriminative power. The overlap coefficient (OVL) between two density functions is defined as the common area between both functions. This coefficient is used as a measure of agreement between two distributions presenting values between 0 and 1, where values close to 1 reveal total overlapping densities. These two measures were used to construct the arrow plot to select differential expressed genes. A simulation study using the bootstrap method is presented in order to estimate AUC bias and standard error using empirical and kernel methods. In order to assess the impact of the OVL variation on the AUC bias, samples from various continuous distributions were simulated considering different values for its parameters and for fixed OVL values between 0 and 1. Samples of dimensions 15, 30, 50, and 100, and 1000 bootstrap replicate for each scenario were considered.
- Bacterial contamination assessment and MRSA colonization in the context of occupational exposure in Portuguese swine productionsPublication . Ribeiro, Edna; Monteiro, AnaOccupational health concern has been increasing worldwide in occupational settings with increased health-associated potential hazards such as direct contact with live animals. Animals, including pigs, are reservoirs of livestock-associated microorganisms, such as methicillin-resistant Staphylococcus aureus (MRSA), potentially linked with subsequent clinical diseases and transference of the infection/colonization to others. Here we aimed to perform a bacterial contamination characterization of the indoor environment and assess S. aureus colonization prevalence, including MRSA, in both workers and animals from five Portuguese swine productions. Nasopharyngeal samples (N=68) were collected and inoculated in non-selective and selective culture media and MRSA isolates were confirmed by immunologic assays. Air samples (50 L) were collected through an impaction method, seeded in TSA and VRBA media and quantitative colony-forming was obtained (CFU.m-3) after incubation. We report an exceptionally high prevalence of total bacteria and MRSA colonization in both workers and animals and demonstrated high air values of total bacterial concentration, potentially associated with a positive selection pressure. This work emphasizes the urge to monitor resistant bacteria strains in occupational contexts to develop proper surveillance programs to determine and regulate the antibiotic selection pressure that is driving the emergence of these resistant strains and the necessity to create occupational standards and take effective preventive measures.
- Avaliação da utilização da sequência 3D-T2w em ressonância magnética biparamétrica no estadiamento do carcinoma da próstataPublication . Castela, Tiago Alexandre Ferreira de; Freire, LuísObjetivos: Avaliar a performance diagnóstica na obtenção um correto estadiamento do carcinoma da próstata, utilizando uma sequência de imagem por RM 3D-T2w, inserida num protocolo de aquisição Biparamétrico. Métodos: Após aprovação institucional e consentimento informado, 22 doentes com diagnóstico confirmado de carcinoma da próstata e indicados para prostatectomia radical robótica, foram examinados num equipamento de RM 3 T, tendo sido utilizadas sequências de imagem 2D-T2w TSE, DWI e 3D-T2w SPACE (validada previamente em fantoma). Seguida a anonimização, randomização e replicação em 4 subgrupos distintos, 2 Uro-Radiologistas avaliaram individualmente cada um dos subgrupos de imagem. Foram obtidas medidas de qualidade por intermédio de uma escala de Likert, bem com estatísticas descritivas, correlações inter-técnica e inter-observador, sensibilidade, especificidade, valor preditivo positivo e valor preditivo negativo, com valores considerados significativos para p < 0,05. Resultados: Os observadores classificaram a qualidade das imagens 3D-T2w como sendo significativamente inferior face às imagens standard 2D-T2w. Verificou-se ainda a ausência de correlação entre os resultados apurados com as imagens 3D-T2w e os resultados da Anatomia Patológica, com uma sensibilidade de apenas 64%. Na avaliação integrada com a DWI, passou a verificar-se correlação com a Anatomia Patológica, e a sensibilidade subiu para 86%, juntamente com uma especificidade de 88%, valor preditivo positivo de 83% e valor preditivo negativo de 100%. Conclusões: A performance diagnóstica das imagens 3D-T2w é inferior à conseguida pelas imagens 2D-T2w, mesmo com a integração no protocolo biparamétrico.
- Estudo do valor de diagnóstico da técnica de ressonância magnética na avaliação funcional da ATM antes e após a artrocentese: revisão sistemática da literaturaPublication . Santilal, Jéssica Gilberto; Freire, LuísA Disfunção temporo-mandibular (DTM) é uma das patologias que envolve complicações na articulação temporo-mandibular (ATM), nos músculos mastigatórios e nas estruturas associadas e que se manifesta na oclusão. As desordens da ATM podem ser do tipo intra- ou extra-articular. O deslocamento do disco, que faz parte das desordens intra-articulares, pode ainda ocorrer com ou sem redução, isto é, durante a abertura máxima da boca, o disco anterior pode, ou não, ficar reduzido. O diagnóstico da DTM envolve a avaliação da história do paciente e a observação clínica deste. Em seguida, podem ser requeridos exames complementares de diagnóstico, os quais incluem geralmente imagens médicas obtidas através das técnicas de Ressonância Magnética (RM) ou de Ultrassonografia. A RM é considerada como a técnica gold standard uma vez que as imagens por ela fornecida permitem analisar a relação do disco com a articulação e com as estruturas associadas, não só no estádio normal, mas também na presença de patologia. Para além disso, esta técnica tem a capacidade de fornecer informações sobre a morfologia e a posição do disco, permitindo a deteção dos primeiros sinais de disfunção, os quais incluem a rutura do tecido retrodiscal. Para o tratamento desta desordem da ATM existem diversas opções terapêuticas de entre as quais se destaca a artrocentese, uma terapia minimamente invasiva e que pode ser usada quando o doente não responde à terapêutica conservativa. O presente trabalho foi realizado com o objetivo de avaliar com que frequência são adquiridas imagens de RM, antes e após a artrocentese, em pessoas com deslocamento do disco articular. Tem ainda como objetivo perceber a relevância dada pelos diferentes autores à realização da imagem de controlo de RM (adquirida após a artrocentese). Para responder aos objetivos, foi efetuada uma revisão da literatura em 4 bases de dados: Pubmed, Cochrane Library, LILACS e ScienceDIrect, com as palavras-chave “arthrocentesis”, “magnetic resonance”, e “disc displacement”. Após a aplicação dos critérios de exclusão, foram incluídos 24 estudos, publicados entre 2014 e 2020. Cada artigo foi analisado através da Newcastle Ottawa Quality Assessment Scale para avaliação da respetiva qualidade. Apesar do número reduzido de estudos, conclui-se que um número reduzido de autores realiza a aquisição de imagens de RM após a artrocentese, o que compromete a avaliação imagiológica dos doentes depois de terem sido submetidos à terapia.