Perceiving audiovisual synchrony as a function of stimulus distance

Dissertação de mestrado integrado em Psicologia (área de especialização em Psicologia Experimental)Audiovisual perception is still an intriguing phenomenon, especially when we think about the physical and neuronal differences underlying the perception of sound and light. Physically, there is a delay of ~3ms/m between the emission of a sound and its arrival to the observer, whereas speed of light makes its delay negligible. On the other hand, we know that acoustic transduction is a very fast process (~1ms) while photo-transduction is quite slow (~50 ms). Nevertheless, audio and visual stimuli that are temporally mismatched can be perceived as a coherent audiovisual stimulus, although a sound delay is often required to achieve a better perception. A Point of Subjective Simultaneity (PSS) that requires a sound delay might point both to a perceptual mechanism that compensates for physical differences or to one that compensates for the transduction differences, in the perception of audiovisual synchrony. In this study we analyze the PSS as a function of stimulus distance to understand if individuals take into account sound velocity or if they compensate for differences in transduction time when judging synchrony. Using Point Light Walkers (PLW) as visual stimuli and sound of steps as audio stimuli, we developed presentations in a virtual reality environment with several temporal alignments between sound and image (-285ms to +300ms of audio asynchrony in steps of 30 ms) at different distances from the observer (10, 15, 20, 25, 30, 25 meters) in conditions which differ in the number of depth cues. The results show a relation between PSS and stimulation distance that is congruent with differences in velocity of propagation between sound and light (Experiment 1). Therefore, it appears that perception of synchrony across several distances is made possible by the existence of a compensatory mechanism for the slower velocity of sound, relative to light. Moreover, the number and quality of depth cues appears to be of great importance in the triggering of such a compensatory mechanism (Experiment 2).A percepção audiovisual é um fenómeno curioso, especialmente quando consideramos as diferenças físicas e neuronais subjacentes à percepção do som e da luz. Fisicamente, há um atraso de cerca de 3 ms/m entre a emissão de um som e a sua chegada ao observador, enquanto a velocidade da luz torna o seu atraso negligenciável. Por outro lado, sabemos que a transdução de um estímulo sonoro é um processo muito rápido (~1 ms) enquanto que a foto-transdução é um processo relativamente lento (~50 ms). Apesar destas diferenças, sabemos que estímulos auditivos e visuais temporalmente desalinhados podem ser percebidos como um estímulo audiovisual coerente. No entanto, para que tal aconteça, um atraso do som em relação à imagem é frequentemente necessário. Um Ponto de Simultaneidade Subjectiva (PSS) que requer um atraso do som pode ser um indício da existência tanto de um mecanismo perceptual que compensa as diferenças físicas, como de um mecanismo perceptual que compense as diferenças neuronais, na percepção de sincronia audiovisual. Neste estudo analisamos o PSS em função da distância de estimulação para perceber se temos em conta a velocidade do som ou se compensamos as diferenças ao nível dos processos de transdução, quando estamos a julgar a sincronia entre um estímulo auditivo e um visual. Usando Point Light Walkers (PLW) como estímulo visual e som de passos como estímulo sonoro desenvolvemos apresentações em ambiente de realidade virtual, com diferentes alinhamentos entre som e imagem (de -285ms a +300ms, em passos de 30 ms, de assincronia do audio) e a várias distâncias do observador (10, 15, 20, 25, 30, 25 metros), em condições que variavam segundo o número de pistas de profundidade apresentadas. Os dados mostram que há uma relação positiva entre PSS e distância de estimulação congruente com as diferenças entre som e luz, ao nível da velocidade de propagação (Experiência 1). Desta forma, parece-nos que a percepção de sincronia audiovisual ao longo de várias distâncias é possível através da existência de um mecanismo de compensação para a velocidade do som, mais lenta em relação à da luz. O número e qualidade das pistas de profundidade parecem também ter uma grande importância na activação deste mecanismo de compensação (Experiência 2)

Temporal variability in winter wave conditions and storminess in the northwest of Ireland

Winter storms have significant morphological impacts in coastal areas, often leading to extensive infrastructure damage and socioeconomic disruption. While storm-dominated coastal environments, such as the northwest coast of Ireland, are generally attuned to highly energetic wave conditions, morphological impacts can be intensified by changes in the frequency and sequencing of storm events, particularly during storm-groups or exceptional winter seasons. Aiming to assess the variability in frequency and sequencing of wintertime wave conditions and storms in the northwest of Ireland, we combine observational records (M4 buoy) with data from two independent wave reanalyses (ERA-Interim and WAVEWATCH III) and perform a statistical analysis of wave conditions over the past six decades. Both reanalyses represent observed wave heights with very good skill. Excellent agreement between modelled data and observations was identified up to the 99th percentile, despite a slight underestimation/ overestimation by ERA-Interim/WAVEWATCH III for waves above the 90% exceedance level. The winter of 2014/15 was the most energetic on record (67 years), but not the stormiest. The results show that highly energetic and stormy winters occur in clusters during positive phases of the North Atlantic Oscillation. Significant positive temporal trends for winter wave height, number of storms per winter and average winter storm wave height, suggest that winters are becoming more energetic and stormier, with potential implications for the erosion and recovery of coastal systems in the northwest of Ireland

Functional characterization of mitochondrial suspensions by cytofluorimetric techniques towards the screening of mitochondrial target drugs

Dissertação de mestrado em Bioquímica AplicadaBesides its role in respiration, mitochondria control other key metabolic pathways, cell proliferation and regulated cell death, with a crucial role in the regulation of the intrinsic apoptotic pathway. Recent studies have focused on the screen for anti-cancer agents that induce apoptosis through permeabilization of the mitochondrial outer membrane, leading to the cytosolic release of pro-apoptotic proteins and to the activation of the caspase cascade and consequently to cell dismantling. In the present study, staining protocols were developed and optimized aiming at the structural and functional characterization of isolated mitochondrial populations from yeast cells and rat liver by flow cytometry. Mitotracker Green and Nonyl Acridine Orange were used to measure changes in mitochondrial mass, 3,3'- Dihexyloxacarbocyanine Iodide and Mitotracker Red CMXROS to monitor the electrical potential of the inner membrane (Δψm), Mitotracker Red CM-H2XROS and Dihydroethidium to evaluate the accumulation of ROS, and 2',7'-Bis-(2-Carboxyethyl)- 5-(and-6)-Carboxyfluorescein and Acetoxymethyl Ester (BCECF-AM) to measure the pH of the mitochondrial matrix. Subsequent flow cytometry studies were designed to evaluate the effect in mitochondria function of two well-known apoptosis inducers in both mammalian cell lines and yeast cells, namely bovine lactoferrin (bLf) and acetate, and to understand whether or not they act directly on mitochondria independently of upstream cellular pathways. The results showed that both bLf and acetate promoted changes in mitochondrial mass, matrix mitochondrial pH, Δψm and ROS levels of rat liver mitochondria. Moreover, the assessment of the activity of the complexes of electron transport chain (ETC) showed that bLf and acetate affect their activity and trigger mitochondrial swelling. These results are particularly interesting since the two compounds appear to induce in isolated mitochondria mainly the same alterations as those occurring in whole cells, and which have been proposed to be involved in the induction of cell death. Altogether, this study show that flow cytometry is a valuable tool to study key mitochondrial functional parameters and to screen for mitochondriatargeted drugs, including the anticancer agents, such as acetate and bLf.Para além do seu papel na respiração celular, as mitocôndrias controlam outros aspetos chaves do metabolismo, bem como a proliferação celular e a morte celular regulada, tendo um papel crucial na regulação da via apoptótica intrínseca. Estudos recentes têm-se focado na procura de agentes anticancerígenos capazes de induzir apoptose mediada pela permeabilização da membrana mitocondrial externa, conduzindo à libertação de proteínas pró-apoptóticas e à ativação da cascata de caspases e consequente desmantelamento celular. No presente estudo, foram desenvolvidos e otimizados protocolos de marcação com vista à caracterização estrutural e funcional por citometria de fluxo de populações de mitocôndrias isoladas de células de levedura e de hepatócitos de rato. As sondas Mitotracker Green e laranja de nonil-acridina foram usadas para medir variações da massa mitocondrial, o iodeto de 3,3'-Dihexiloxacarbocianina e o Mitotracker Red CMXROS para medir o potencial eléctrico da membrana mitocondrial interna (Δψm), o Mitotracker Red CM-H2XROS e dihidroetídeo para avaliar a acumulação de ROS e o acetoximetil éster de (2',7'-Bis-(2- Carboxietil)-5-(and-6)-carboxifluoresceína e(BCECF-AM) para medir o pH da matriz mitocondrial. Os estudos subsequentes de citometria de fluxo foram desenhados para avaliar o efeito de diferentes drogas na função mitocondrial, em particular da lactoferrina bovina (bLf) e do acetato, dois reconhecidos indutores de apoptose, no sentido de se compreender se atuam diretamente na mitocôndria independentemente de outras vias celulares a montante. Os resultados mostraram que tanto a bLf como o acetato promovem alterações na massa mitocondrial, pH da matriz mitocondrial, Δψm e nos níveis de ROS em mitocôndrias isoladas de fígado de rato. Além disso, a avaliação da atividade dos complexos da cadeia de transportadora de eletrões (ETC) mostrou que a bLf e o acetato afetam a sua atividade e desencadeiam a tumefação mitocondrial. Estes resultados são particularmente interessantes uma vez que os dois compostos parecem induzir, em mitocôndrias isoladas as mesmas alterações que ocorrem em células inteiras, e que têm sido propostas como estando envolvidas na indução da morte celular. No seu conjunto, este estudo mostra que a citometria de fluxo é uma ferramenta valiosa para o estudo da funcionalidade mitocondrial e para o rastreio de drogas que têm como alvo a mitocôndria, incluindo agentes anticancerígenos, tais como a bLf e o acetato

Prediction of overwash in alongshore variable barrier islands [Previsão da ocorrência de galgamentos em ilhas barreira com variabilidade longilitoral]

Overwash prediction is very important for coastal zone management. This work intends to identify alongshore variations in storm impact and evaluate the role of sub-aerial and submerged morphologies in overwash occurrence. For this study, 24 cross-shore topo-bathymetric profiles were set on Barreta Island (Ria Formosa barrier island system, Portugal). Pre- and post-overwash surveys were made between August 2012 and April 2013. During overwash events, tidal levels and wave parameters at breaking were obtained. Overwash occurred under storm and non-storm conditions, the latter coincident with spring high-tide. Beach morphology was spatially variable, and changeable from one overwash episode to the next. Predictions of overwash occurrence were made using the Overwash Potential, defined as the difference between runup and barrier elevation. Several runup equations were tested, and the results compared to the actual observations. The selected predictor provided an accuracy of 88% for the identification of the locations where overwash occurred. This study proves that nearshore and foreshore morphologies have a major impact on the longshore distribution of overwash.info:eu-repo/semantics/publishedVersio

Modelling of estuarine response to sea-level rise during the Holocene: Application to the Guadiana Estuary–SW Iberia

This paper focuses on simulations of the morphological evolution of an estuary during sedimentary infilling that accompanied Holocene sea-level rise. The simulations were conducted using the Estuarine Sedimentation Model, which uses a behaviour-oriented approach, supported by the chronostratigraphy of the estuary's sedimentary sequence. Behaviour curves were computed to represent the relationship between the estuarine channel depth below maximum high tide and the net accretion at a given location relative to the average sedimentation rate of the estuary during the Holocene. The model was validated by comparing the observed present-day bathymetry of the Guadiana River Estuary, southeastern Portugal, with the corresponding simulated bathymetries for nine control sections across the estuary. The best fit between simulated and actual sediment surface elevations was obtained along the cross-sections in the sheltered, low-energy environments of the estuary. The accuracy of the sedimentary stratigraphy of the best-fit model was further established using 16 radiocarbon ages obtained from five boreholes in the estuary. The present approach is particularly suitable for simulating long-term morphological evolution in sheltered estuarine environments where tidally driven vertical aggradation dominates at centennial to millennium timescales. However, the accuracy of simulated sediment surface elevations and consequently the robustness of behaviour-type models based on Geographical Information System platforms can be enhanced by incorporating (i) the impacts of nearshore hydrodynamic processes and episodic flood events in highly energetic channels, and (ii) the impacts of cross-currents in meandering channel sections. (C) 2015 Elsevier B.V. All rights reserved.FCT [SFRH/BD/70747/2010, SFRH/BPD/85335/2012

Morphologic change and morphodynamics at high-energy embayed beaches in Southwestern Portugal

Along the southwestern coast of Portugal, a high-energy, swell dominated environment with a markedly seasonal wave climate, morphologic change in three embayed beaches was regularly monitored over a two year period. While a general seasonal pattern was identified, the occurrence of a storm group induced dramatic beach response, producing marked interannual variability. Significant spatial variations in behaviour emerged during the monitoring period, inducing alongshore non-uniform beach change within each embayment. Megarips were the prevailing mechanism responsible for the extreme erosion experienced in all three beaches, and their specific location (controlled by topography) contributes to the variability observed within each beach. Despite severe beach erosion, dunes were unaffected, which suggests long-term stability of these high-energy, dissipative, embayed coastlines

Morphological and economic impacts of rising sea levels on cliff-backed platform beaches in Southern Portugal

Projections from the Intergovernmental Panel on Climate Changes (IPCC) point to a global mean sea level rise (SLR) of close to 1 m by 2100 for a worst-case scenario. This will have a significant impact on coastal areas worldwide, primarily by modifying the shoreline position and coastal morphology, but also by influencing the coastal economy and livelihoods. Generally, it is assumed that sandy barriers will adapt to SLR through shoreline retreat and barrier inland migration. However, for embayed beaches backed by cliffs and/or underlined by shore platforms, constraints to inland migration will compromise such morphological response, with SLR-induced shoreline retreat leading to reductions in beach width and area. This will have impacts on beach use and carrying capacity. Aiming to analyse the morphological changes induced by SLR at cliff-backed platform beaches, this study explores simple mathematical models to quantify beach morphological change. 2D cross-shore profiles, representing the morphology of the beach and the underlying shore platform, were analysed using two geometric models of beach profile response. The model of Taborda and Ribeiro (2015) was applied for profiles with berm, while a new model is proposed for profiles without berm. The models assume that for profiles with berm there is both retreat and rise of the berm, while for profiles without berm the beach face becomes steeper and the sub-aerial beach narrower in response to SLR. Using a high-resolution topo-bathymetric LiDAR dataset, 94 cross-shore profiles from 32 beaches in southern Portugal were analysed. Their evolution was modelled considering the IPCC RCP8.5 scenario, which projects a SLR between 0.5 m and 1 m by 2100. From the 48 profiles with berm, 15 will experience complete berm erosion by 2100 for a 1 m SLR worst case scenario. The modelled average berm/beach width reduction is 7.9/5.8 m and 9.5/9.6 m for a SLR of 0.5 m and 1 m, respectively. A total of 26 beaches will become steeper and may be submerged if a threshold equilibrium beach slope is exceeded. Changes to the beach carrying capacity due to reduction in beach area will impact the local and regional economy, since the southern coast of Portugal is strongly influenced by beach tourism. The modelled changes to beach area result in a maximum potential economic loss ranging between EUR 215,000 and EUR 561,000 per day during peak summer months if no mitigation measures are considered. Beach nourishment was found to be a cost-effective measure to prevent the modelled reduction in beach area and mitigate the associated economic impacts

Integrating information systems success and overall trust

Tam, C., Loureiro, A., & Oliveira, T. (2020). The individual performance outcome behind e-commerce: Integrating information systems success and overall trust. Internet Research, 30(2), 439-462. [Advanced online publication on 22 october 2019]. https://doi.org/10.1108/INTR-06-2018-0262Purpose: While most e-commerce studies focus on the understanding of online customer behaviour, mainly adoption and purchase behaviours. The purpose of this paper is to examine the relationship between e-commerce and individual performance. The authors test the role of systems, information and service quality in e-commerce use and user satisfaction. Trust may become an important aspect for a consumer’s decision making, based on this the authors identify the effect of the role of trust on e-commerce use, user satisfaction and its impact on individual performance. This research has theoretical and managerial implications, since the protagonism of e-commerce is increasing in both academia and industry. Design/methodology/approach: The authors apply a research model that integrates information systems success dimensions and user behaviour in the form of trust. The empirical approach was based on an online survey questionnaire of 437 individuals from Portugal. Findings: The results reveal that overall quality and overall trust are important to explain use and user satisfaction in the context of e-commerce, which further leads to individual performance. The findings indicate that a higher level of use and user satisfaction increase individual performance. Originality/value: The authors integrate information systems success dimensions and overall trust to understand the significance of e-commerce individual performance. The authors expect the results to enrich the understanding of the importance of considering both technological and behavioural factors to increase the success of e-commerce.authorsversionpublishe

Towards a simulation-based medical education platform for PVSio-web

Interface design flaws are often at the root cause of use errors in medical devices. Medical incidents are seldom reported, thus hindering the understanding of the incident contributing factors. Moreover, when dealing with a use error, both novices and expert users often blame themselves for insufficient knowledge rather than acknowledge deficiencies in the device. Simulation-Based Medical Education (SBME) platforms can provide appropriate training to professionals, especially if the right incentives to keep training are in place. In this paper, we present a new SBME, particularly targeted at training interaction with medical devices such as ventilators and infusion pumps. Our SBME functions as a game mode of the PVSio-web, a graphical environment for design, evaluation, and simulation of interactive (human-computer) systems. An analytical evaluation of our current implementation is provided, by comparing the features on our SBME with a set of requirements for game-based medical simulators retrieved from the literature. By being developed in a free, open source platform, our SBME is highly accessible and can be easily adapted to specific use cases, such a specific hospital with a defined set of medical devices.Jose Campos work was supported by project "NORTE-01-0145-FEDER-000016" financed by the North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF). Carlos Silva work was supported by grant no. POCI-01-0145-FEDER-031943, co-financed by COMPETE2020 under the PT2020 programme, and supported by FEDER. The authors wish to thank Paolo Masci, developer of PVSio-web, for extensive support and input