Dor psicológica e ideação suicida em estudantes

Mestrado em Psicologia Clínica e da SaúdeOs estudantes do Ensino Superior, especificamente do curso de Enfermagem (pela sua conhecida natureza multifacetada), apresentam níveis de ansiedade mais elevados quando comparados com outros, sendo a licenciatura de Enfermagem aquela que reúne condições mais susceptíveis para ser considerada ameaçadora e de certa forma indutora de stresse para os seus estudantes. Quando estes níveis de stresse são percebidos negativamente ou se tornam excessivos (distress psicológico), podem afetar não só a realização académica como a saúde mental dos estudantes, provocando sintomas depressivos e uma significativa dor psicológica que pode despoletar no jovem adulto pensamentos, desejos e até mesmo planos para terminar com tal sofrimento (Ideação Suicida). O presente estudo teve como objetivo, avaliar a depressão, o distress psicológico, especificamente a dor psicológica e ideação suicida em estudantes de Enfermagem da Escola Superior de Enfermagem de Coimbra, ESEnfc, comparando estes diferentes níveis com os diferentes anos académicos. A amostra é constituída por 776 alunos, com idades compreendidas entre os 17 e os 58 anos (M=20.78; DP=3.14). Esta amostra respondeu a um protocolo composto por um Questionário Sóciodemográfico; o Questionário de Saúde do Paciente PHQ-SADS, o Inventário de Sintomas Psicopatológicos BSI e a Escala da Dor Psicológica. De acordo com os resultados obtidos, verificou-se ser o sexo feminino, aquele que possui valores mais elevados de distress e depressão. Desta forma, também são as raparigas que apresentam maiores níveis de dor psicológica comparativamente com o sexo oposto, o que está relacionado com a forma como estas encaram o ensino superior, desde a entrada até à permanência no mesmo, provocando concomitantemente uma maior percentagem de respostas verdadeiras nas questões relacionadas com a ideação suicida. Importante será referir que é no 1º e 4º ano da licenciatura que se verificam níveis mais elevados de distress, sendo o 3º ano aquele que pontua valores mais baixos em todas as variáveis. São sugeridos novos estudos no âmbito do ensino superior, mais especificamente nas áreas de saúde, para revelar quais os motivos pelos quais estes valores mantém-se elevados. Seria útil implementar um programa de prevenção junto dos alunos logo na fase de ingresso ao Ensino Superior, de forma a melhor lidar com a ansiedade, diminuindo a dor psicológica dos mesmos e dessa forma prevenir a ideação suicida e possível suicidio consumado nesta população.Students in Higher Education, specifically in the nursing course (known for its multifaceted nature), have higher levels of anxiety when compared with others, also the degree in Nursing congregates conditions most likely to be considered threatening and somehow stress inducing to their students. When these stress levels are perceived negatively, or become excessive (psychological distress), they can affect not only academic achievement but also mental health of the students, causing significant depressive symptoms and psychological pain that may trigger the adult thoughts, desires and even plans to end such suffering (Suicidal Ideation). The present study aimed to assess depression, psychological distress, more specifically psychological pain and suicidal ideation in nursing students from the Nursing School of Coimbra, ESEnfC, comparing these levels in the different academic years. The sample consisted of 776 students, aged 17 to 58 years (M = 20.78, SD = 3.14). This sample responded to a protocol which contains a sociodemographic questionnaire, the Patient Health Questionnaire PHQ-SADS, Psychopathological Symptom Inventory BSI and Psychological Pain Scale. According to the results, females have higher levels of distress and depression. Thus, they also have higher levels of psychological pain compared with the opposite sex. This could be related to how they perceive higher education, from the entrance to the residence in the same, concomitantly causing a higher percentage of responses true in matters related to suicidal ideation. Importantly is to be noted that in the 1st and 4th year of the degree is the higher levels of distress occur. Also, the 3rd year reveals lower values for all variables. It is necessary to undertake further studies in the framework of higher education, specifically in health related courses, in order to explore more thoroughly the motives of the resukts. Moreover, futher studies may contribute to a better implementation of prevention programs among students at the beginning of their entrance to Higher Education in order to avoid future anxiety disorders and psychological pain, and also prevent possible suicide ideation suicide attempts

Characterization of HIV-2 susceptibility to protease and entry inhibitors and identification of envelope determinants of coreceptor usage, cell tropism and antibody neutralization

Tese de doutoramento, Farmácia (Microbiologia), Universidade de Lisboa, Faculdade de Farmácia, 2018The main aim of this work was to characterize the susceptibility of HIV-2 to protease and entry inhibitors and to identify viral determinants of coreceptor usage, cellular tropism and antibody neutralization. The specific objectives were: 1) to determine the contribution of amino acids residues in the V3 loop involved in CCR5 and CXCR4 use, susceptibility to antibody neutralization and cellular tropism; 2) to develop a genotypic method for the prediction of HIV-2 coreceptor usage based on V3 loop; 3) to evaluate the antiviral activity of a new short-peptide fusion inhibitor in HIV-2 and 4) to characterize the evolution and diversity of protease (PR) in HIV-2 infected patients treated and untreated with protease inhibitors (PIs). In the first study (Chapter 3), site-directed mutagenesis was used to create amino acid substitutions in residues 18 and/or 29 and/or single deletions at positions 23 and 24 in V3 loop of pROD10, an infectious molecular clone of HIV-2ROD, the reference X4 isolate. Cellular assays demonstrated that: 1) conversion from X4 to R5 phenotype in HIV-2ROD10 requires H18L substitution and the deletion Δ(23,24); 2) H18L and H23Δ + Y24Δ mutants are more easily neutralized than HIV-2ROD and other mutated viruses by plasma from HIV-2 infected individuals; on the other hand, K29T substitution seems to contribute to increase resistance to neutralization; 3) K29T mutants acquire macrophage tropism without compromising replicative capacity in CD4+ T lymphocytes; 4) H18L + Δ(23,24) and (23,24) mutants gained the ability to replicate in macrophages albeit at the cost of some capacity to replicate in CD4+T cells. Structural analysis by homology modelling showed that: 1) H18L substitution disrupts the interaction of histidine with methionine at position 15 and with phenylalanine at position 20; 2) deletion of H23 and Y24 leads to the elimination of the parallel β sheets presented in the V3 loop and the loss of the aromatic system which can compromise the binding of cellular coreceptors or other molecules (e.g. antibodies); 3) K29T substitution reduces the charge of V3 and leads to the loss of the interactions with isoleucine at position 27. Collectively, these results demonstrated that V3 is an important determinant in HIV-2 coreceptor usage, susceptibility to antibody neutralization and replication capacity on CD4+ T cells and macrophages and that these phenotypic characteristics can be modulated by a single amino acid change in V3. These results support an important role for V3 in the pathogenesis of HIV-2 infection. In the second study (Chapter 4), a genotypic method was developed for the prediction of HIV-2 coreceptor usage from the V3 loop, similar to an existing tool created for HIV-1 (geno2pheno [coreceptor-hiv2]). The development and validation of this tool was based on a data set of 126 samples from HIV-2 infected patients, most of them from Portugal, with phenotypic coreceptor usage annotations. Predictive accuracy was also validated based on the V3 mutants produced and phenotypically characterized in the previous chapter. Overall, these findings indicated that geno2pheno [coreceptor-hiv2] can be a useful tool in clinical practice, allowing better management of HIV-2 infected patients eligible for maraviroc (MVC). In the third study (Chapter 5) a short-peptide named 2P23 was produced by combining a M-T hook structure, HIV-2 sequences and ‘salt-bridge’-based strategies. This peptide showed a potent antiviral activity against HIV-2 and HIV-1 isolates (mean 50% inhibitory concentration- IC50: 20.17 nM and 5.57 nM, respectively) and SIV (IC50: 1.8 nM for SIVpbj and 3.29 for SIV239). This new fusion inhibitor also demonstrated a strong activity against the V3 variants (Chapter 3) (IC50:15.38 nM), irrespectively of the coreceptor phenotype. Thus, 2P23 is an ideal candidate for further clinical development due to its broad antiviral activity against several HIV-2 isolates, with different coreceptor tropism. The last study (Chapter 6), involved the characterization of PR diversity and genotypic resistance to PIs of HIV-2 infected individuals living in Portugal and the evaluation of the impact of resistance mutations to PIs in treatment outcome eight years post-therapy. A high prevalence of PR mutations (e.g. I54M, I82F, L90M) associated to saquinavir (SQV), darunavir (DRV) and lopinavir (LPV) resistance, were detected in proviral DNA from these patients at baseline. Eight years after study entry, the genotypic analysis identified: 1) loss of resistance mutations in two patients, that were initially detected at baseline, presumably as a consequence of treatment interruption; 2) long term persistence of resistance mutations in one individual as a result of virologic and immunologic failure, which might raise concern about transmission of drug resistance in the future and 3) development of new resistance mutations in three patients due to previous treatment failures. The analysis of genetic diversity in PR showed an increase in this parameter in two treated patients, with undetectable viral loads and higher CD4+ T counts, comparing with the baseline. On the other hand, a reduction in PR genetic diversity was exhibited in three patients (two treated and one untreated), who presented detectable viral loads in at least one time point during the follow up. Due to small sample size it was not possible to investigate a potential relationship between PR genetic diversity and CD4+ T cell counts, presence of resistance mutations or/and treatment status. However, these results seem to indicate a persistent viral replication during long term highly active antiretroviral therapy (HAART), regardless of plasma viral load. The maintenance of viral replication can act as a source of new proviral quasispecies, resulting in the gradual substitution of the ancestral variants over time. Most importantly, we found two potential cases of transmitted drug resistance. However, due to the small sample size, additional studies with a higher number of patients are required to determine if primary drug resistance is a major problem in HIV-2 infected patients in Portugal. Our findings suggest that proviral DNA may be useful in resistance testing in HIV-2 patients with low or suppressed viremia and in untreated patients, and that early resistance analysis of these archived viruses may predict treatment response

Seismic behaviour of masonry veneer walls

Tese de Doutoramento em Civil EngineeringIt is recognized that masonry veneer walls, commonly used in commercial, industrial and residential buildings can be vulnerable to earthquakes and most of the reported cases of failures are due to poor materials, design and inadequate construction practices. This inadequate behaviour has promoted research on the seismic behaviour of brick veneer walls mostly attached to structural systems composed of light timber and steel frames but this work aims to contribute to the knowledge of seismic behaviour of masonry veneer whose backing support is composed by brick masonry infill walls enclosed in RC frames that is a construction system common in Portugal and South of European countries. In detail, this thesis aims at: (1) analyse at the local level the mechanical behaviour of connections of wall ties between the brick veneer walls and masonry infill walls; (2) assess the mechanical behaviour of brick veneer walls under out-of-plane loads for different configurations of ties; (3) carry out an overview of standards and provide design and construction guidelines under seismic action for brick masonry veneer walls. To accomplish this, an extensive experimental program was designed, being divided mainly in two phases: (1) mechanical and physical characterization of materials components, such mortar, bricks and brick masonry. An extensive experimental campaign on cyclic tension-compression and shear tests on different tie-masonry assemblages was performed. Different parameters were considered, namely the type of tie, width of the air cavity, mortar strength and embedment length of the ties; (2) cyclic out-of-plane tests on brick masonry veneer walls attached to brick masonry walls enclosed in a RC frame. In this experimental campaign it was also varied the type of ties, air cavity width, embedment length and the effect of previous in-plane loading. The experimental work is complemented with analytical tools to define hysteric laws to represent the cyclic tension-compression and shear behaviour of ties, which can be used in further numerical studies. It was concluded that the tension-compression behaviour of connections is influenced by the type of wall tie and air cavity width. The stiffness of tie and free length influences significantly the compression behaviour and the shape of tie and embedment length of the tie control the tensile behaviour. The out-of-plane behaviour of the brick veneer walls depend also on the type and number of ties, and on the air cavity width. Both parameters control the out-of-plane performance from the brick veneer walls to the backing wall.As paredes de alvenaria de fachada, habitualmente aplicadas em edifícios comerciais, industriais e residenciais, podem ser vulneráveis a terremotos e a maioria dos casos de rotura registados deve-se a materiais pobres, projeto e práticas inadequadas de construção. Esse comportamento inadequado tem promovido investigação sobre o comportamento sísmico de paredes de alvenaria de fachada principalmente conectadas a sistemas estruturais constituídos por madeira e estruturas metálicas. Este trabalho visa compreender o comportamento sísmico de paredes de fachada, cujo suporte é composto por paredes de enchimento inseridas em pórticos de betão armado, sendo um sistema de construção comum em Portugal e no sul da Europa. Em detalhe, esta tese pretende: (1) analisar localmente o comportamento mecânico das conexões com ligadores entre a parede de fachada e a parede de enchimento; (2) avaliar o comportamento mecânico de paredes de alvenaria de fachada sob carregamento fora do plano em diferentes configurações de conexões; (3) desenvolver uma revisão de normas e fornecer diretrizes de projeto e construção para paredes de alvenaria de fachada. Com efeito, foi desenvolvido um extenso programa experimental, sendo dividido principalmente em duas fases: (1) caracterização mecânica e física dos componentes do sistema, tais como argamassas, tijolos e alvenaria. Foi realizada uma extensa campanha experimental de ensaios cíclicos de tração-compressão e corte em diferentes tipos de conexões. Consideraram-se diferentes parâmetros, nomeadamente o tipo de ligador, a largura da cavidade de ar, a resistência da argamassa e o comprimento de embebimento dos ligadores; e (2) ensaios cíclicos fora de plano em paredes de alvenaria de fachada ligadas a paredes de enchimento inseridas em pórticos de betão armado. Nesta campanha experimental também foi avaliado o tipo de ligador, a largura da cavidade de ar, o comprimento de embebimento e efeito de dano prévio no plano. O trabalho experimental foi complementado com ferramentas analíticas para definição de leis histeréticas para a representação do comportamento de compressão-tração e corte das conexões, que podem ser usadas em estudos numéricos adicionais. Concluiu-se que o comportamento de compressão-tração das conexões é influenciado pelo tipo de ligador da parede e pela largura da cavidade de ar. A rigidez do ligador e o comprimento livre influenciam significativamente o comportamento à compressão. O tipo de ligador e o comprimento de embebimento do ligador controlam o comportamento à tração. O comportamento fora do plano das paredes de alvenaria depende também do tipo e número de ligadores e da largura da cavidade de ar. Ambos os parâmetros controlam o desempenho fora do plano das paredes de alvenaria de fachada e da parede de suporte.Fundação para a Ciência e Tecnologia (FCT) - Pelo financiamento através da Bolsa de Doutoramento SFRH/BD/96484/2013. Este trabalho foi parcialmente financiado pelos fundos FEDER através do Programa Operacional Fatores de Competitividade - COMPETE e pelos fundos nacionais da FCT no âmbito do projeto POCI-01-0145-FEDER-0076 3

Comparing the cluster efficiency of fragmental-periodogram and fragmented-ACF

Mestrado Bolonha em Mathematical FinanceBig data faz, cada vez mais, parte do nosso dia a dia e tem um impacto cada vez maior na nossa sociedade. Tem entusiasmado os investigadores para encontrarem novos métodos para lidar com conjuntos de dados muito grandes. Na análise das séries temporais, a mesma necessidade surge. Há algumas décadas, os investigadores batalhavam para encontrar séries de dados longas o suficiente para as analisar; hoje em dia, estão frequentemente sobrecarregados com conjuntos de dados que são demasiado grandes para lidar com métodos tradicionais. O objetivo deste trabalho é estudar e propor métodos para medir as semelhanças e diferenças entre diferentes séries temporais. Esses métodos devem ser computacionalmente simples e perdem, naturalmente, algumas informações, mas devem ser capazes de fornecer métricas que são adequadas para agrupar grandes conjuntos para extensas séries temporais. Para ser mais específica, estudo um método muito recente chamado periodograma fragmentado e confirmo por simulação, a sua utilidade para fornecer uma medida simples que leva ao agrupamento correto das séries temporais em consideração. Esta replicação dá al- gum conforto quanto à correção do exercício e leva a uma descoberta interessante sobre as regras de fragmentação. Portanto, proponho um método equivalente no domínio do tempo, o ACF fragmentado, e confirmo por simulação a sua utilidade. Finalmente, comparo os dois métodos e concluo que o ACF fragmentado tem um desempenho comparável, senão superior. As simulações são, naturalmente, limitadas a classes particulares de modelos, o que abre espaço para pesquisas futuras, como discuto na secção final.Big data is increasingly having a large impact on our society and prompting researchers to find novel methods to deal with very large data sets. In time series analysis, the same need arises. A few decades ago, researchers were struggling to find long enough data series for their analysis; nowadays, they are often overwhelmed with data sets that are too large to handle with traditional methods. The aim of this work is to study and propose methods for measuring the similarities and dissimilarities among different time series. These methods should be computationally simple and naturally lose some information, but they should be able to provide metrics that are suitable for clustering large sets on long time series. To be more specific, I study a very recent method called fragmented periodogram and confirm by simulation its usefulness to provide a simple measure that leads to correct clustering of the time series under consideration. This replication gives some comfort as to the correctness of the exercise and leads to an interesting finding regarding the fragmenting rules. Then, I propose an equivalent method in time domain, the fragmented ACF and confirm by simulation its usefulness. Finally, I compare the two methods and conclude that the frag- mented ACF has a comparable if not superior performance. The simulations are naturally limited to particular classes of models, which opens room for further research, as I discuss in the final section.info:eu-repo/semantics/publishedVersio

Joining of steel to aluminium alloys for advanced structural applications

When joining steel to aluminium there is a reaction between iron and aluminium which results in the formation of brittle intermetallic compounds (IMC). These compounds are usually the reason for the poor mechanical strength of the dissimilar metallic joints. The research on dissimilar metal joining is vast but is mainly focused on the automotive industry and therefore, the material in use is very thin, usually less than 1 mm. For materials with thicker sections the present solution is a transition joint made by explosion welding which permits joining of steel to aluminium and avoids the formation of IMCs. However, this solution brings additional costs and extra processing time to join the materials. The main goals of this project are to understand the mechanism of formation of the IMCs, control the formation of the IMCs, and understand their effects on the mechanical properties of the dissimilar Fe-Al joints during laser welding. Laser welding permits accurate and precise control of the welding thermal cycle and thereby the underpinning mechanism of IMC formation can be easily understood along with the factors which control the strength of the joints. The further goal of this project is to find an appropriate interlayer to restrict the Fe-Al reaction. The first stage of the work was focused on the formation and growth of the Fe-Al IMCs during laser welding. The understanding of how the processing conditions affect the IMC growth provides an opportunity to act and avoid its formation and thereby, to optimize the strength of the dissimilar metal joints. The results showed that even with a negligible amount of energy it was not possible to prevent the IMC formation which was composed of both Fe2Al5 and FeAl3 phases. The IMC growth increases exponentially with the applied specific point energy. However, for higher power densities the growth is more accentuated. The strength of the Fe-Al lap-joints was found to be not only dependent on the IMC layer thickness but also on the bonding area. In order to obtain sound joints it is necessary to achieve a balance between these two factors. The thermal model developed for the laser welding process in this joint configuration showed that for the same level of energy it is more efficient to use higher power densities than longer interaction iv times. Even though a thicker IMC layer is formed under this condition due to higher temperature there is also more melting of aluminium which creates a larger bonding area between the steel and the aluminium. The joint strength is thus improved ... [cont.]

Does trade credit facilitate access to bank finance?: an empirical evidence from Portuguese and Spanish small medium size enterprises

This paper examines if trade credit could be considered as a substitute and/or a complement to bank credit in order to assess the existence of credit rationing. Using a panel dataset of 468 and 7019 Portuguese and Spanish small medium size enterprises, in the period 1998-2006, and controlling for endogeneity problems by using GMM estimators, the results confirm the existence of credit rationing, since the substitution hypothesis is confirmed. This effect is particularly strong for firms that maintaining an exclusive relationship with one bank, which indicate a greater severity of adverse selection problems for those firms. Although the substitution hypothesis is confirmed, the results seem indicate that the substitution and complementary hypothesis are not mutually exclusive, especially for a specific group of firms: the younger and smaller firms. In line with the theories that emphasize the informational role of trade credit, due the informative advantage of suppliers, our empirical results confirm that trade credit allow the younger and smaller firms to improve their reputation, as trade credit reveals the private information of the supplier to the bank, in turn, banks can update their beliefs about customer default risk and agree to increase bank credit.O objectivo deste trabalho de investigação consiste em analisar se o crédito comercial obtido junto dos fornecedores e o endividamento bancário são considerados duas fontes de financiamento substitutas e/ou complementares. Usando uma amostra em dados painel de 468 e 7019 pequenas e médias empresas (PME) Portuguesas e Espanholas respectivamente, e recorrendo ao método de estimação GMM, para controlar potenciais problemas de endogeneidade, os resultados confirmam a hipótese de substituição, isto é, as empresas recorrem ao crédito junto dos fornecedores quando vêm restringido o seu acesso ao financiamento junto dos bancos. Este racionamento no acesso ao crédito bancário é particularmente relevante para as empresas que mantêm uma relação de monopólio (negoceiam com apenas um banco), o que indicia maiores problemas de selecção adversa e risco moral para estas empresas. Todavia, apesar de a hipótese de substituição ser confirmada, a evidência empírica aponta para o facto de que as hipóteses de substituição e complementaridade não serem mutuamente exclusivas, em particular para um grupo específico de empresas: as empresas mais jovens e mais pequenas. Em consonância com as teorias que enfatizam o conteúdo informativo veiculado pelo crédito comercial (qualidade da gestão, nível de risco do cliente), os resultados obtidos confirmam que o recurso ao crédito concedido pelos fornecedores ajuda as empresas mais jovens e mais pequenas a consolidarem a sua reputação no mercado de crédito. O montante de crédito comercial obtido pode ser visto como um sinal que veicula a informação privada detida pelo fornecedor aos bancos a baixo custo. Neste contexto, os bancos mostram-se mais predispostos a conceder crédito

Novel processes for extraction and fractionation of fatty acids from microbial cell mass

In this thesis a novel integrated process for extraction and fractionation of long chain polyunsaturated fatty acids (LC-PUFA), particularly the high-value docosahexaenoic acid (DHA), from wet microbial cell mass was investigated. The research was focused in two main aspects: (i) selection of enzymes for stepwise hydrolysis of triacylglycerols present the cell mass, and (ii) evaluation of a biphasic membrane contactor system, comprising an asymmetric membrane, for extraction of released fatty acids. The kinetics of hydrolysis of triacylglycerols to diacylglycerols, monoacylglycerols and free fatty acids for specific and non-specific lipases was characterised. It was demonstrated that the enzymatic hydrolysis of triacylglycerols can be effectively performed directly in the cell mass suspension, i.e. without previous isolation of the lipid fraction. New analytical methods were developed for the analyses of acylglycerols and fatty acids by LC-ESI-MS. The access to the concentration profiles of tri-, di-, and monoacylglycerols throughout the reaction enabled a better evaluation of the performance of enzymes tested in terms of kinetics and selectivity. An effective selective hydrolysis can be attained by employing specific and non-specific lipases in the enzymatic hydrolysis of triacylglycerols. Based on the results obtained, optimum combinations of enzymes for process applications can be proposed. Asymmetric polyimide membranes were prepared and tested for the separation of fatty acids in the biphasic membrane contactor system. It was found that the type of polymer, the membrane molecular weight cut-off, and the composition of the aqueous phase all had considerable effect on mass transfer across the membrane. Significantly higher mass transfer coefficients of long-chain fatty acids than previously reported were achieved. The solute transport mechanism through asymmetric polyimide porous membranes in the biphasic system was also explored. However, the membrane mass transfer coefficients calculated based on the solute transport model proposed, did not explain experimental observations well. The feasibility of the proposed integrated process for sequential enzymatic hydrolysis of triacylglycerols and simultaneous separation of released fatty acids was demonstrated. As expected, the presence of an emulsion in the aqueous phase limited the mass transfer through the membrane. However, promising results were observed, and mass transfer rates may be improved by further optimisation of the operating conditions. It is then concluded that the objective of the present work was accomplished as a partial fractionation of the main fatty acids was obtained.Open Acces

Catálogo do espólio documental de Joaquim Magalhães (1909-1999)

Um acervo pessoal de natureza documental reflete sem qualquer sombra de dúvidas, a vivência e criatividade pessoais, profissionais e académicas do seu possuidor/autor. E um acervo pessoal com a dimensão e a diversidade do acervo do Dr. Joaquim Peixoto Magalhães é sem sombra de dúvida de uma riqueza intelectual assinalávelFundação Calouste Gulbenkia

Avaliação ecográfica da morfologia muscular perante situações de sobrecarga agudas e crónicas

Introduction: Ultrasound (US) has an important role in musculoskeletal (MSK) evaluation, allowing the study of muscle morphology and function. Muscle thickness (MT) and muscle echo-intensity (EI) are two important parameters that may quantify muscle structural adaptations to a variety of stimuli. US elastography can also offer semi-quantitative and/or quantitative assessment of tissue stiffness providing relevant information about adaptations of muscle mechanical properties. Purpose: The general aim of the studies presented in this thesis is to explore the potential of quantitative US imaging for assessing the adaptations and responses of the muscle tissue to increased contractile activity using B-mode US and US elastography. The studies were centred on the quadriceps femoris muscle and addressed the study of the effect of strength training and of acute muscle contractile activity on MT, EI and muscle stiffness. Materials and methods: Three different studies were conducted and reported along this thesis. A total of 64 young adults of both genders participated in the studies. The first study (N = 20) evaluated the intra- and inter-session (one week apart) reproducibility of MT and EI parameters and the role of plane of view (transverse vs. longitudinal) and ROI dimension on measurements’ accuracy using the intraclass correlation coefficient [ICC(3,1)], the standard error of measurement (SEM), and the smallest detectable change (SDC). Bland-Altman analysis was used to study the level of agreement between plane views and ROI sizes. The second study (N = 28) investigated the effect of a 15-week strength program on MT and EI in several regions of the heads of the quadriceps femoris. This study included a control group and two training groups performing concentric or eccentric strength training. During this study, changes in vastus lateralis’ (VL) stiffness in response to strength training were evaluated using quasi-static elastography (QSE). In the final study (N = 16), acute changes in VL’s stiffness associated with passive stretching, performance of short but intense contractile activity, and muscle isometric contractions were investigated by means of supersonic shear wave imaging (SSI). Results: Moderate to very high reliability was found for MT (intra-session, ICCs: 0.82- 0.99; inter-session, ICCs: 0.70-0.98) and EI (intra-session, ICCs: 0.74-0.97; inter-session, ICCs: 0.48-0.94). In general, reliability for MT and EI measures was higher in the transverse plane and when using a larger ROI, respectively. Measurements of EI taken with a small versus a large ROI are associated with a small bias and larger limits of Morphological ultrasound evaluation in acute and chronic muscle overloading agreement (LoA). In study 2, 15 weeks of strength training increased MT in the majority but not in all of the scanned regions. Strength training failed in changing EI in most of the quadriceps femoris, excepting in the VI and some regions of the VL. Strength training significantly increased VL’s stiffness. No differences were observed in our quantitative US parameters between concentric and eccentric training. The final study demonstrated an acute increase of around 10% in VL’s shear modulus as a result of performing maximal isometric, concentric, and eccentric contractions. The shear modulus of the VL also increased when the knee moved from 10º to 50º and then to 90º flexion. Finally, a linear relationship between the shear modulus and the level of isometric muscle contraction was observed. Conclusions: Ultrasound measures of MT and EI show moderate to very high reliability. The reliability and agreement of MT and EI measurements are improved in transverse scans and with larger ROIs. QSE could demonstrate an increase in muscle stiffness as a result of strength training. SSI proved to be a good method to investigate muscle mechanical properties changes associated with muscle function. These results emphasise the value of an objective and quantifiable muscle US evaluation for studying muscle adaptation to exercise training and muscle function, in general.Introdução: A ultrassonografia tem um papel importante na avaliação músculoesquelética, permitindo o estudo da morfologia e função muscular. A espessura muscular e a eco- intensidade muscular são dois parâmetros importantes que podem quantificar as adaptações estruturais musculares, quando o musculo é submetido a determinados estímulos. A elastografia por ultrassonografia pode, também, oferecer uma avaliação semi-quantitativa e/ou quantitativa da rigidez do tecido, fornecendo informações relevantes sobre as adaptações das propriedades mecânicas musculares. Objetivo: O objetivo geral, dos estudos apresentados nesta tese, é explorar o potencial da imagem quantitativa ultrassonográfica, de forma a avaliar as adaptações e as respostas do tecido muscular ao aumento da atividade contrátil, usando a elastografia e a ultrassonografia em modo-B. Os estudos foram centrados no músculo do quadricípite femoral e abordaram o estudo do efeito do treino de força e da atividade contrátil muscular na espessura muscular, eco-intensidade e rigidez muscular. Materiais e métodos: Três diferentes estudos foram realizados e descritos ao longo desta tese. Um total de 64 jovens adultos de ambos os géneros participaram dos estudos. No primeiro estudo (N = 20), foi analisada a reprodutibilidade da espessura muscular e da eco-intensidade dos quatro músculos que compõem o quadricípite femoral. Para isso foram adquiridas três imagens em modo B, nos planos longitudinal e transversal, em dois momentos distintos. A eco-intensidade foi medida usando dois tamanhos diferentes de região de interesse, um representado por uma forma retangular, medindo 70 mm2 e um outro representando o máximo do músculo apresentado na imagem ultrassonográfica, evitando as fáscias superficial e profundas do mesmo. A precisão das medidas foi, então, analisada usando o Coeficiente de correlação intra-classe [ICC (3,1)], o erro padrão de medição (SEM) e a menor alteração detectável (SDC). A análise de Bland-Altman foi utilizada para estudar o nível de concordância entre os planos de imagem ultrassonográficos e os diferentes tamanhos da região de interesse. No segundo estudo (N = 28), analisou-se o efeito de um programa de treino de força, com duração de 15 semanas, sobre espessura muscular e ecointensidade em três diferentes regiões de cada um dos quatro músculos que representam o quadricípite femoral: reto femoral, vasto intermédio, vasto medial e vasto lateral. Este estudo incluiu um grupo de controlo e dois grupos de treino, em que um realizou um protocolo de treino concêntrico e o outro de treino excêntrico. Durante este estudo, as alterações na rigidez do vasto lateral, em resposta ao treino de força foram avaliadas usando a elastografia quasi-statica, semi-quantitativa. No último estudo (N = 16), foram analisadas as alterações agudas na rigidez de vasto lateral associadas ao alongamento passivo, ao desempenho de atividade contrátil de curta duração, mas intensa e às contrações isométricas musculares usando a elastografia de onda supersónica por cisalhamento. Resultados: Foi encontrada uma alta ou muito alta reprodutibilidade para espessura muscular (intra-sessão, ICCs: 0,82-0,99; inter-sessão, ICCs: 0,70-0,98) e eco-intensidade (intra-sessão, ICCs: 0,74-0,97; inter-sessão, ICCs: 0,48-0,94). Em geral, a reprodutibilidade para os valores da espessura muscular foi maior no plano transversal e no que diz respeito aos valores da eco-intensidade verificou-se uma melhor reprodutibilidade quando foi utilizada uma região de interesse de maiores dimensões. Um pequeno viés e menores valores de concordância caracterizam as medidas de cointensidade obtidas com uma região de interesse maior ou menor. No estudo 2, os participantes submetidos a 15 semanas de treino de força revelaram o aumento da sua espessura na maioria das regiões musculares avaliadas, mas não em todas. Não foram encontradas alterações significavas dos valores da eco-intensidade com a realização do treino de força na maioria dos músculos do quadricípite femoral, excepto para o vasto intermédio e para algumas regiões do vasto lateral.Por outro lado, o treino de força aumentou significativamente a rigidez do vasto lateral. Não foram observadas diferenças significativas nos parâmetros quantitativos ultrassonográficos entre o treino concêntrico e excêntrico. O último estudo demonstrou um aumento agudo de cerca de10% nos valores da rigidez do vasto lateral como resultado da realização de contrações máximas isométricas, concêntricas e excêntricas. Os valores da rigidez do vasto lateral também aumentaram durante a flexão do joelho de 10º para 50º e posteriormente para 90º. Finalmente, observou-se uma relação linear entre os valores de rigidez do vasto lateral e o nível de contração muscular isométrica do quadricípite femoral. Conclusões: As medidas ultrassonográficas da espessura muscular e eco-intensidade mostram uma reprodutibilidade moderada a muito alta. A reprodutibilidade e a concordância das medidas de espessura muscular e eco-intensidade são maiores no plano transversal e quando é utilizada uma região de interesse de maior dimensão. A elastografia semi-quantitativa mostrou existir um aumento significativo na rigidez muscular como resultado do treino de força. A elastografia por onda de cisalhamento supersónica é um bom método para investigar as alterações das propriedades mecânicas musculares associadas à função muscular. Estes resultados enfatizam a importância de uma avaliação objetiva e quantificável dos músculos por ultrassonografia, para estudar a adaptação muscular ao treino e função muscular, no geral