Latent growth mixture modeling: an application in the aeronautic training environment

The application of growth mixture modeling to longitudinal data offers an important extension of conventional modeling tools, enabling the identification of different patterns in growth, by accounting for population heterogeneity. The main goal of this study is to analyze the shape of the learning process in pilot training (Latent Growth Modeling), as well as to recognize different patterns in growth due to population heterogeneity (Growth Mixture Modeling). Moreover, the research intends to identify predictors that explain that variability and the pattern of growth. The object of study is the performance in flight training of ab-initio pilot applicants (n=297) to the Portuguese Air Force Academy (evaluated through six repeated measures). The results showed the existence of unobserved heterogeneity in the population and the best fitting model is a 2-class mixture model. Psychomotor coordination (SMA) showed a significant effect on the intercept (initial status) and the prognostic of General Adaptability (Personality and Motivation dimension) depicted a significant effect on the intercept (initial status) and on slope (development). The latent class 1 (66% of the sample) presents the highest initial flight performance, a positive significant effect of the General Adaptation on the intercept and the best results in the tests performed in the psychological phase. The latent class 2 (34% of the sample) presents the worst initial flight performance, and a positive significant effect of General Adaptation on the slope.A aplicação de modelo de mistura com crescimento latente a dados longitudinais oferece uma generalização importante dos modelos de crescimento convencionais, permitindo a identificação de diferentes padrões de crescimento, tendo em conta a heterogeneidade da população. O principal objectivo deste estudo consiste em analisar o processo de aprendizagem no treino de pilotos (modelos com crescimento latente), identificar diferentes padrões de crescimento resultantes da heterogeneidade existente (modelo de mistura com crescimento latente), e identificar as variáveis explicativas da variabilidade e do padrão de crescimento. O objecto de estudo é o desempenho no treino de pilotos ab-initio (n=297), candidatos à Academia da Força Aérea Portuguesa (avaliados em seis medidas repetidas). Os resultados obtidos demonstram que existe heterogeneidade não observada na população e que o modelo mais adequado é um modelo de mistura com crescimento latente de duas classes. A coordenação motora (SMA) demonstrou um efeito significativo no intercepto (estado inicial) e o prognóstico de Adaptabilidade Geral (dimensão Personalidade/Motivacional) demonstrou um efeito significativo quer no intercepto (estado inicial) quer no declive (aprendizagem). A classe latente 1 (66% da amostra) caracteriza-se por apresentar uma performance em voo superior no estado inicial (intercepto), um efeito significativo da Adaptabilidade Geral no intercepto, e melhores resultados nos testes realizados na fase de avaliação psicológica. Por sua vez, a classe latente 2 (34% da amostra) apresenta piores resultados relativos ao estado inicial da performance em voo, e um efeito significativo da Adaptabilidade Geral na aprendizagem (declive)

Echinoderm Biodiversity and Biogeography in Oceanic Islands: the Azores as a case study

Oceanic Islands are natural laboratories for the study of the processes and patterns of dispersion, colonization and ultimately of the appearance of new species. In the Northeast Atlantic, the archipelago of the Azores meets all the requirements to be considered one of the most isolated oceanic island systems. In general terms, the Azorean biota, as other oceanic systems, derives from dispersal chance events. For shallow-water marine benthic organisms, the main mechanisms to overcome the isolation by distance are rafting by non-planktonic life stages and through planktonic larval stages, both of which rely heavily on sea-surface currents to travel. However, and in spite of being under the influence of the western-intensified Gulf Current, the Azorean biota shows an opposite trend, being predominantly derived from the NE Atlantic and the Mediterranean. This apparent paradox has startled many marine biogeographers, who search for answers in the present-day faunal patterns together with those reconstructed through the past geological history of the archipelago. The present study attempts to further contribute to the knowledge of the marine fauna of the Azores, and its biogeographical relationships, using the echinoderms as a model. This animal phylum encloses a diverse group of strictly marine invertebrates found at all latitudes and depths. Furthermore, the echinoderms form one of the most conspicuous elements of both shallow- and deep-sea fauna in the Azores, and both in extant waters and among the fossiliferous outcrops of Santa Maria (37°N23’ 24°45’W), the oldest island in the archipelago. Thus, for a clear biogeographical background it was necessary to construct an updated catalogue of both local extant and fossil echinoderm fauna. During the International Workshops ‘Palaeontology in Atlantic Islands’, held in Santa Maria Island between 2002-2013, new material was collected from Lower Pliocene and Pleistocene deposits. The early Pliocene beds encompass the following taxa: Eucidaris tribuloides, Echinoneus cf. cyclostomus, Clypeaster altus, Echinocyamus pusillus, Echinocardium sp. 1, Echinocardium sp. 2, Schizobrissus sp. and undetermined spatangoids. The Pleistocene outcrops (MISS 5e) included three regular echinoid species, Sphaerechinus granularis, Arbacia lixula and Paracentrotus lividus. The small irregular echinoid Echinocyamus pusillus was also present in the Azorean Pleistocene fauna, a species common as well in the extant coasts of the archipelago. The presence of tropical taxa in the early Pliocene sediments clearly contrasts with the warm temperate taxa found in the Pleistocene and present coasts of the Azores. Updated faunal lists are fundamental in biodiversity and biogeographical studies. Arbaciella elegans is a small cryptic echinoid species that was believed to have a large geographical range from the tropical Atlantic waters of Central Africa to the northern shores of the Azores, Canaries, Northwest Africa and Mediterranean Sea. However, and unlike the Central African material, individuals from the warm temperate waters present a uniform dark color. A morphological and genetic characterization of specimens from the Azores shows that the dark Arbaciella phenotype represents in fact juvenile stages of Arbacia lixula, which implies that A. elegans is circumscribed to the tropical African waters from where it was first described. This study emphasizes the difficulty of constructing faunal lists mirroring true distributions of species or local biodiversity, when rare or cryptic species are involved. The Faculty of Sciencie and Tecnology (University of the Azores), houses hundreds of echinoderm specimens collected over more than 20 years of activity by the former Department of Biology. Three young specimens of the Mediterranean sea star Sclerasterias richardi (Perrier, in Milne-Edwards, 1882), a species previously not known to the Azores, were found among the echinoderm material. These animals were dredged off the south coast of São Miguel Island, at 135 m depth. Sclerasterias richardi is one of two sea star species known to reproduce asexually through fission in the Azores, the other being the shallow-water Coscinasterias tenuispina (Lamarck, 1816). However, S. richardi, though a shelf species, lives at much deeper waters than the latter. S. richardi is also capable of producing long-lived planktotrophic larvae with high dispersal potential to reach remote areas such as the Azores. The presence of S. richardi in Azorean waters in an otherwise thoroughly investigated area does not necessarily imply a recent arrival, as the depths in consideration (80-700 m) are also the least studied in the archipelago. The review of the extant echinoderm fauna of the Azores, based on the related bibliography that has been accumulating over 150 years, complemented with the construction of an important local echinoderm reference collection in the University of the Azores, resulted in a critical reassessment of this significant component of the Azorean marine fauna. Herein are reported 172 species of echinoderms (6 crinoids, 55 ophiuroids, 45 asteroids, 36 holothuroids and 30 echinoids) to the archipelago, most of them inhabiting deep-waters. Although 65 species could be classified as shelf species (840 m) appear to be restricted to the Azorean waters. Though relatively poorer in number of species, the Azores show similar general trends to what is observed in other Macaronesian archipelagos (i.e. Madeira, Canaries and Selvagens): lack of endemic species, dominance of echinoderm fauna generally associated with rocky shores and species capable of producing planktonic feeding larvae. The relatively low echinoderm diversity could be attributed to the archipelago remoteness, the northern geographical position and to other local features attributed to their relative young volcanic age (e.g., lower habitat diversity). The echinoderm fauna of the Azores encompasses several edible species, though none known to be traditionally harvested. In recent years, fisheries targeting holothurian species have developed dramatically in several European and North African countries, and two of the most common sea-cumber species in the Azores, Holothuria mammata and H. sanctori, are now being commercially harvested in the Northeast Atlantic and in the Mediterranean Sea. The identification of Holothuria species tends to be difficult and time-consuming, and in many cases requires experienced taxonomists. Conversely, the use of PCR-RFLPs to rapidly and inexpensively identify species with no need for taxonomical or genetic expertise could prove a valuable asset. The present work introduces a simple and fast method, using restriction nuclease Sau3AI on 16S rRNA fragments. A simple non-destructive DNA sampling is also presented, using tube feet or oral tentacles, to be applied in genetic studies. The updated faunal list of the echinoderms of the Azores was combined with those from the other areas in an updated distributional catalogue of the shallow-water echinoderms (≤200 m depth) from the North and Central Atlantic, and the Mediterranean Sea, providing the basic framework for the analysis of biodiversity patterns and the construction of a biogeographical model. A total of 891 species belonging to 341 genera of shallow-water echinoderms are presently recorded in the studied areas. The tropical West Atlantic was by far the most biodiverse region (483 species, 210 of which were endemic). The Mediterranean Sea did not emerge as a biodiversity hotspot, revealing similar biodiversity rates as the neighbouring regions of Iberian and NW Africa, but presented significant endemism rate. Among the insular systems, Canaries presented the highest echinoderm biodiversity with 85 species, followed by Cabo Verde with 76. A positive correlation between latitude and the species’ depth range was detected, confirming the Rapoport’s latitudinal gradient. The most common larval development was planktotrophic (119 species), followed by the lecithotrophic (71 species) and aplanktonic (47 species). The relative representation of lecithotrophic and aplanktonic larval development increased towards high latitude areas and decreased as species geographical range increased. Also, the asexual reproduction decreased towards high latitude colder areas and this reduction was correlated with the relative increase of aplanktonic larval mode of development in the same areas. Endemic species were particularly numerous among sediment-associated habitats and broadly distributed species showed no preference for either soft or hard bottoms. Most areas showed a natural decrease of shared species with increasing geographical distance and this was particularly evident in oceanic systems. In these, faunal affinities tended to be related with the nearest continental shores, regardless of the prevailing sea-surface currents. In general, echinoderms proved to be good models for testing biodiversity and biogeographical patterns, though significant gaps were found on the available information

Novel dynamics and functions of Fibronectin in early vertebrate development

The metameric body plan of vertebrates is established during somitogenesis, one of the most complex morphogenetic events during development. Somites epithelialize periodically from the anterior-most presomitic mesoderm, and this rhythmicity is thought to be controlled by cyclic traveling waves of gene expression that sweep the tissue anteriorly. Although the spatial and temporal regulation of somitogenesis has been extensively studied, how the periodicity of genetic oscillations is translated into periodic somite epithelialization remains elusive. Furthermore, while knockout experiments have implicated the extracellular matrix component fibronectin in somite formation, much of the roles of its qualitative features deriving from its assembly state are still unknown. The aim of this thesis is to re-address the role of fibronectin during paraxial mesoderm development, particularly during somite morphogenesis. In Chapter 2, we describe fibronectin production and assembly dynamics during early embryogenesis and found that it is highly dynamic throughout paraxial mesoderm development, as different forms of fibronectin assembly (autocrine vs paracrine) correlate with exquisite morphogenetic events. In Chapter 3 we re-address the role of fibronectin during somite formation in vivo. We show that an intact fibronectin matrix and downstream mechanotransduction signaling are required for correct segmentation clock dynamics and somite morphogenesis. Our results suggest that the fibronectin matrix and its downstream chemical and mechanical cues couple genetic oscillations with timely somite morphogenesis. In Chapter 4 we investigate the role of fibronectin in somite maturation. We demonstrate that normal fibronectin assembly is required for correct Sonic hedgehog signaling in the somite, which in turn controls fibronectin production in this tissue, suggesting that fibronectin and Sonic cooperate to orchestrate somite patterning and differentiation. This thesis demonstrates that fibronectin is a dynamic pivotal player regulating paraxial mesoderm development. It also highlights the previously unappreciated importance of the extracellular matrix and its derived mechanical cues during embryonic development.O padrão metamérico do plano corporal dos vertebrados é estabelecido na somitogénese, um dos mais complexos eventos morfogenéticos do desenvolvimento. Os sómitos epitelizam a partir da parte anterior da mesoderme pré-somítica de forma periódica, num processo controlado por ondas cíclicas de expressão génica que percorrem este tecido numa direcção posterior-anterior. Embora muitos estudos se tenham focado no controlo temporal e espacial da somitogénese, os mecanismos pelas quais estas oscilações genéticas se traduzem na morfogénese periódica dos sómitos são em grande parte desconhecidos. Por outro lado, foi demonstrado que a matriz extracelular de fibronectina é crucial à formação dos sómitos, mas o impacto das suas características qualitatitvas neste processo é também desconhecido. Esta tese tem como objectivo reavaliar o papel da fibronectina durante o desenvolvimento da mesoderme paraxial, em particular na morfogénese dos sómitos. No Capítulo 2, analisamos a dinâmica de produção e montagem da fibronectina durante o desenvolvimento precoce, demonstrando que a montagem da matriz de fibronectina é extremamente dinâmica durante as várias fases de desenvolvimento da mesoderme paraxial, correlacionando com o seu rearranjo e maturação. No Capítulo 3 analisamos o papel da matriz de fibronectina na formação de sómitos in vivo, mostrando que esta matriz e respectiva mecanotransdução são cruciais para a dinâmica do relógio de segmentação e morfogénese do sómito. Estes resultados apontam a matriz de fibronectina como o agente responsável à coordenação das oscilações genéticas com a formação periódica do sómito. No Capítulo 4, mostramos que a matriz de fibronectina é necessária à sinalização Sonic hedgehog nos sómitos, que por sua vez controla a produção de fibronectina neste tecido, sugerindo que ambos colaboram na padronização e diferenciação do sómito. Os resultados desta tese demonstram que a fibronectina tem um papel fundamental na regulação do desenvolvimento da mesoderme paraxial, e evidencia a importância da matriz extracelular no desenvolvimento

Burnout em enfermeiros no início da carreira

Tese de mestrado, Psicologia (Secção de Psicologia dos Recursos Humanos, do Trabalho e das Organizações), 2009, Universidade de Lisboa, Faculdade de Psicologia e de Ciências da EducaçãoEste trabalho analisa as percepções de enfermeiros em início de carreira em relação às Exigências Quantitativas e Emocionais, Controlo e Burnout em dois momentos temporais, espaçados de 6 meses. Usado o modelo de JD-C de Karasek como modelo explicativo para a ocorrência de Burnout, formulámos a hipótese de que os enfermeiros com menos tempo de serviço percepcionavam maiores Exigências, menor Controlo e, consequentemente, maiores sintomas de Burnout do que os enfermeiros com mais tempo de serviço. As mesmas percepções foram analisadas 6 meses mais tarde com o intuito de detectar, por hipótese, menor percepção de Exigências, maior Controlo e menor Burnout. A partir de uma amostra de 249 enfermeiros de um Hospital de Lisboa, concluiu-se que os enfermeiros com menos de um ano de serviço sentem uma maior Dissonância Emocional e maior Despersonalização na relação com os pacientes. Ao fim de 6 meses, estes enfermeiros apesar de sentiram uma diminuição da Despersonalização, sentiram um aumento da Exaustão. A Dissonância Emocional manteve-se constante. Estes resultados sugerem que a implementação de um programa de adaptação que aborde a questão da Dissonância Emocional é importante para melhorar a adaptação e integração profissional dos enfermeiros no início de carreira.This work analyzes the perception of nurses in the beginning of their career with regard to Emotional and Quantitative Demands, Control and Burnout in two moments in time, 6 months apart. Using the JD-C Karasek model of Burnout, we hypothesize that nurses with smaller service time perceive higherDemands, less Control and higher Burnout symptoms with regard to nurses with longer service time. Thesame perceptions were analyzed 6 months later to detect, by hypothesis, smaller perception of EmotionalDemands, smaller Control and smaller Burnout. From a sample of 249 nurses in an Hospital in Lisbon,we have concluded that subjects with smaller service time feel different Emotional Demands thansubjects with higher service time, in the form of higher Emotional Dissonance, the same perception ofControl and higher Burnout, through a higher Depersonalization. After 6 months, these subjects felt adecrease in Depersonalization and an increase of exhaustion, a dimension of Burnout. EmotionalDissonance remained constant. These results suggest that the implementation of an adaptation programthat faces Emotional Dissonance is important to improve the feeling of Depersonalization within nurses at the start of their career

The influence of NWOM in the consumers’ decision-making process in the Tourism industry

Online feedback tools, such as electronic Word-of-Mouth (eWOM), have been widely used to share knowledge and information online between consumers about products or services, having become an important tool for consumers and being considered a reliable source. Based on relevant theories and previous works, it has been proved that Negative Word-of-Mouth (NWOM) has been influencing significantly consumers’ decision-making process, especially regarding the Tourism industry and that this sector is the most strongly influenced by eWOM. To investigate the impact of NWOM on consumers in the industry of Tourism, an online survey was created. Different negative hotel reviews were presented to 249 individuals. Quantitative data was generated to investigate the impact of these reviews on consumers’ brand attitude, purchase intentions and NWOM intentions, in two distinct stages of the travel planning process, namely the search phase vs the post-purchase phase, when a new purchase was being planned. The conclusions supported the existence of a significant impact of NWOM on users that are exposed to negative reviews in the Tourism sector. Furthermore, users in the post-purchase phase were less susceptible to NWOM than those in the search phase, which means that NWOM communication mostly affects consumers who are in the search phase of the travel planning process. This study contributes to companies, especially hotels, by identifying useful research that can help them understanding the power of negative information on consumers, taking advantage of online consumer reviews as a new marketing tool. Finally, limitations are discussed and future research is proposed.Ferramentas de feedback online, como o electronic Word-of-Mouth (eWOM), têm sido amplamente utilizadas para partilhar conhecimento e informação online entre consumidores sobre produtos ou serviços, tendo-se tornado uma ferramenta importante para os consumidores e sendo considerada uma fonte de informação confiável. Com base em teorias relevantes e trabalhos prévios, o Word-of-Mouth negativo (NWOM) tem influenciado significativamente o processo de tomada de decisão dos consumidores, especialmente na indústria do Turismo, sendo o sector mais influenciado por eWOM. Para avaliar o impacto do NWOM nos consumidores na indústria do Turismo, foi criado um questionário online. Foram apresentadas diferentes comentários negativos sobre um hotel a 249 indivíduos. Obtiveram-se dados quantitativos com o intuito de investigar o impacto destes comentários na atitude dos consumidores, intenção de compra e intenção de NWOM, em duas fases distintas - a fase de pesquisa e a fase de pós-compra, quando uma nova compra estava a ser planeada. As conclusões suportam a existência de um impacto significativo da NWOM sobre aqueles que estão expostos a comentários negativos no setor do Turismo. Além disso, os utilizadores numa fase de pós-compra são menos suscetíveis a NWOM do que aqueles que se encontram numa fase de pesquisa do planeamento de uma viagem. Este estudo contribui para empresas, especialmente hotéis, uma vez que, identificada a importância da comunicação NWOM, surge a possibilidade de uma nova ferramenta de marketing baseada no conteúdo online gerado pelos consumidores. Finalmente, limitações são discutidas e pesquisa futura é proposta