2018
Autores
Ferreira, TD; Silva, NA; Guerreiro, A;
Publicação
PHYSICAL REVIEW A
Abstract
Optical analog experiments have captured a lot of interest in recent years by offering a strategy to test theoretical models and concepts that would be otherwise untestable. The approach relies on the similarity between the mathematical model for light propagation in nonlinear optical media and the model to be mimicked. In particular, the analogy between light and a quantum fluid with superfluidlike properties has been studied extensively. Still, while most of these studies use thermo-optical media to perform these experiments, the possibility of using nematic liquid crystals to perform such optical analog experiments remains to be analyzed. This work explores how this medium can constitute an alternative to materials more commonly used in optical analogs, such as thermo-optical media, and how its tunable properties can be advantageous to explore and better control fluidlike properties of light. Moreover, we explore the analogy between the propagation of light and a quantum fluid, and propose a pump-probe experiment to measure the dispersion relation of the superfluid analog.
2018
Autores
Rodrigues, PP; Ferreira Santos, D; Silva, A; Polonia, J; Ribeiro Vaza, I;
Publicação
ARTIFICIAL INTELLIGENCE IN MEDICINE
Abstract
In pharmacovigilance, reported cases are considered suspected adverse drug reactions (ADR). Health authorities have thus adopted structured causality assessment methods, allowing the evaluation of the likelihood that a drug was the causal agent of an adverse reaction. The aim of this work was to develop and validate a new causality assessment support system used in a regional pharmacovigilance centre. A Bayesian network was developed, for which the structure was defined by experts while the parameters were learnt from 593 completely filled ADR reports evaluated by the Portuguese Northern Pharmacovigilance Centre medical expert between 2000 and 2012. Precision, recall and time to causality assessment (TTA) was evaluated, according to the WHO causality assessment guidelines, in a retrospective cohort of 466 reports (April-September 2014) and a prospective cohort of 1041 reports (January-December 2015). Additionally, a simplified assessment matrix was derived from the model, enabling its preliminary direct use by notifiers. Results show that the network was able to easily identify the higher levels of causality (recall above 80%), although struggling to assess reports with a lower level of causality. Nonetheless, the median (Q1:Q3) ITA was 4 (2:8) days using the network and 8 (5:14) days using global introspection, meaning the network allowed a faster time to assessment, which has a procedural deadline of 30 days, improving daily activities in the centre. The matrix expressed similar validity, allowing an immediate feedback to the notifiers, which may result in better future engagement of patients and health professionals in the pharmacovigilance system.
2018
Autores
Sultan, MS; Martins, N; Costa, E; Veiga, D; Ferreira, MJA; Mattos, S; Coimbra, MT;
Publicação
BIOMEDICAL ENGINEERING SYSTEMS AND TECHNOLOGIES (BIOSTEC 2017)
Abstract
Rheumatic heart disease is the result of damage to the heart valves, more often the mitral valve. The heart valves leaflets get inflamed, scarred and stretched which interrupts the normal blood flow, resulting into serious health condition. Measuring and quantifying clinically relevant features, like thickness, mobility and shape can help to analyze the functionality of the valve, identify early cases of disease and reduce the disease burden. To obtain these features, the first step is to automatically delineate the relevant structures, such as the anterior mitral valve leaflet, throughout the echocardiographic video. In this work, we proposed a near real time method to track the anterior mitral leaflet in ultrasound videos using the parasternal long axis view. The method is semi-automatic, requiring a manual delineation of the anterior mitral leaflet in the first frame of the video. The method uses mathematical morphological techniques to obtain the rough boundaries of the leaflet and are further refined by the localized active contour framework. The mobility of the leaflet was also obtained, providing us the base to analyze the functionality of the valve (opening and closing). The algorithm was tested on 67 videos with 6432 frames. It outperformed with respect to the time consumption (0.4 s/frame), with the extended modified Hausdorff distance error of 3.7 pixels and the improved tracking performance (less failure).
2018
Autores
Tahsir Ahmed Munna, M; Muhammad Allayear, S; Mohtashim Alam, M; Shah Mohammad Motiur Rahman, S; Samadur Rahman, M; Mesbahuddin Sarker, M;
Publicação
International Journal of Engineering & Technology
Abstract
2018
Autores
Leitao, C; Domingues, MF; Novais, S; Tavares, C; Pinto, J; Marques, C; Antunes, P;
Publicação
BIOPHOTONICS: PHOTONIC SOLUTIONS FOR BETTER HEALTH CARE VI
Abstract
Cardiovascular diseases are the main cause of death in the world and its occurrence is closely related to arterial stiffness. Arterial stiffness is commonly evaluated by analysing the arterial pulse waveform and velocity, with electromechanical pressure transducers, in superficial arteries such as carotid, radial and femoral. In order to ease the acquisition procedure and increase the patients comfort during the measurements, new optical fibre techniques have been explored to be used in the reliable detection of arterial pulse waves, due to their small size, high sensitivity, electrical isolation and immunity to electromagnetic interference. More specifically, fibre Bragg gratings (FBGs) are refractive index modulated structures engraved in the core of an optical fibre, which have a well-defined resonance wavelength that varies with the strain conditions of the medium, known as Bragg wavelength. In this work, FBGs were embedded in a commercial resin, producing films that were used to assess the arterial pulse in superficial locations such as carotid, radial and foot dorsum. The technique proved to be a promising, comfortable and trustworthy way to assess the arterial pulses, with all the optical fibre use advantages, in a non-intrusive biomedical sensing procedure. Examples of possible applications of the developed structures are smart skin structures to monitor arterial cardiovascular parameters, in a stable and reliable way, throughout daily activities or even during exams with high electromagnetic fields, such as magnetic resonance imaging.
2018
Autores
Rocio, Vitor; Marcos, Adérito;
Publicação
InforAberta 2018 - VIII Jornadas de Informática da Universidade Aberta
Abstract
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