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Publicações

2018

End-to-End Adversarial Retinal Image Synthesis

Autores
Costa, P; Galdran, A; Meyer, MI; Niemeijer, M; Abràmoff, M; Mendonça, AM; Campilho, A;

Publicação
IEEE TRANSACTIONS ON MEDICAL IMAGING

Abstract
In medical image analysis applications, the availability of the large amounts of annotated data is becoming increasingly critical. However, annotated medical data is often scarce and costly to obtain. In this paper, we address the problem of synthesizing retinal color images by applying recent techniques based on adversarial learning. In this setting, a generative model is trained to maximize a loss function provided by a second model attempting to classify its output into real or synthetic. In particular, we propose to implement an adversarial autoencoder for the task of retinal vessel network synthesis. We use the generated vessel trees as an intermediate stage for the generation of color retinal images, which is accomplished with a generative adversarial network. Both models require the optimization of almost everywhere differentiable loss functions, which allows us to train them jointly. The resulting model offers an end-to-end retinal image synthesis system capable of generating as many retinal images as the user requires, with their corresponding vessel networks, by sampling from a simple probability distribution that we impose to the associated latent space. We show that the learned latent space contains a well-defined semantic structure, implying that we can perform calculations in the space of retinal images, e.g., smoothly interpolating new data points between two retinal images. Visual and quantitative results demonstrate that the synthesized images are substantially different from those in the training set, while being also anatomically consistent and displaying a reasonable visual quality.

2018

Reliable hybrid small-signal modeling of GaN HEMTs based on particle-swarm-optimization

Autores
Hussein A.S.; Jarndal A.H.;

Publicação
IEEE Transactions on Computer Aided Design of Integrated Circuits and Systems

Abstract
This paper presents an efficient parameter extraction method applied to GaN high electron mobility transistors. The procedure only relies on S-parameter measurements at cold bias conditions to extract the extrinsic parameters of a 19-element small-signal model. Hybrid technique of particle-swarm-optimization and direct fitting has been developed and implemented. The extraction procedure has been optimized to consider measurements uncertainty and improve the reliability of the extraction. The procedure has been validated by multibias extraction for different device sizes. A very good agreement between simulations and measurements has been obtained.

2018

Editorial 13

Autores
Cavique, Luís;

Publicação
Revista de Ciências da Computação

Abstract
Apresentamos o mais recente número da Revista de Ciências da Computação. As primeiras palavras de agradecimento vão para os autores, para os membros do conselho editorial encarregues das revisões científicas e para os revisores de língua portuguesa e inglesa. É com tristeza que retiramos o nome do falecido colega Jaime Remédios do conselho editorial. Os artigos estão organizados por ordem de chegada. O primeiro artigo, vindo na continuidade do número anterior, trata de um projeto didático para a programação paralela distribuída. O segundo artigo, de um recente mestre desta universidade, trata uma curiosa aplicação de algoritmos conhecidos na seleção de recursos humanos. O terceiro e quarto artigo, de licenciados recentes desta universidade, tratam respetivamente o planeamento de ações e a visualização de redes. Finalmente, o quinto artigo, apresenta uma nova métrica para a acessibilidade de velocípedes. Se houver solicitações por parte dos leitores, este número terá uma edição em papel disponível na Amazon com o título Revista de Ciências das Computação nº13. Entretanto, convidam-se os autores a submeter trabalhos originais em língua portuguesa ou inglesa para o próximo número da Revista das Ciências da Computação da Universidade Aberta.

2018

Experimental and Theoretical Evaluation of the Trapping Performance of Polymeric Lensed Optical Fibers: Single Biological Cells versus Synthetic Structures

Autores
Paiva, JS; Ribeiro, RSR; Jorge, PAS; Rosa, CC; Azevedo, MM; Sampaio, P; Cunha, JPS;

Publicação
BIOPHOTONICS: PHOTONIC SOLUTIONS FOR BETTER HEALTH CARE VI

Abstract
Optical Tweezers (OTs) have been widely applied in Biology, due to their outstanding focusing abilities, which make them able to exert forces on micro-sized particles. The magnitude of such forces (pN) is strong enough to trap their targets. However, the most conventional OT setups are based on complex configurations, being associated with focusing difficulties with biologic samples. Optical Fiber Tweezers (OFTs), which consist in optical fibers with a lens in one of its extremities are valuable alternatives to Conventional Optical Tweezers (COTs). OFTs are flexible, simpler, low-cost and easy to handle. However, its trapping performance when manipulating biological and complex structures remains poorly characterized. In this study, we experimentally characterized the optical trapping of a biological cell found within a culture of rodent glial neuronal cells, using a polymeric lens fabricated through a photo-polymerization method on the top of a fiber. Its trapping performance was compared with two synthetic microspheres (PMMA, polystyrene) and two simple cells (a yeast and a Drosophila Melanogaster cell). Moreover, the experimental results were also compared with theoretical calculations made using a numerical model based on the Finite Differences Time Domain. It was found that, although the mammalian neuronal cell had larger dimensions, the magnitude of forces exerted on it was the lowest among all particles. Our results allowed us to quantify, for the first time, the complexity degree of manipulating such "demanding" cells in comparison with known targets. Thus, they can provide valuable insights about the influence of particle parameters such as size, refractive index, homogeneity degree and nature (biologic, synthetic). Furthermore, the theoretical results matched the experimental ones which validates the proposed model.

2018

ECIR 2018: Text2Story Workshop - Narrative Extraction from Texts

Autores
Jorge, A; Campos, R; Jatowt, A; Nunes, S; Rocha, C; Cordeiro, JP; Pasquali, A; Mangaravite, V;

Publicação
SIGIR Forum

Abstract
The 1st International Workshop on Narrative Extraction from Texts (Text2Story 2018) was held in conjunction with the 40th European Conference on Information Retrieval, ECIR 2018, Grenoble on the 26 th March 2018. The workshop aimed to help foster the collaboration of researchers on a wide range of multidisciplinary issues related to the text-to-narrativestructure. The program consisted of two keynote talks, six research presentations, a poster session and a slot for demo presentations. This report briefly summarizes the workshop. More information about the workshop is available at http://text2story18.inesctec.pt

2018

Outcome measurement-a scoping review of the literature and future developments in palliative care clinical practice

Autores
Antunes, B; Rodrigues, PP; Higginson, IJ; Ferreira, PL;

Publicação
ANNALS OF PALLIATIVE MEDICINE

Abstract
The aim of this scoping review is to give an overview and appraisal of the development of outcome measurement throughout time and its present importance to healthcare and specifically to palliative care clinical practice. It is based on a search and search results of a published systematic review on implementing patient reported outcome measures in palliative care clinical practice. Medline, PsycInfo, Cumulative Index to Nursing and Allied Health Literature, Embase and British Nursing Index were systematically searched from 1985. Hand searching of reference lists for all included articles and relevant review articles was performed. A total of 3,863 articles were screened. Sixty were included in this scoping review. Outcome measurement has a long history in health care and some of the strongest advocates were Florence Nightingale for using patient outcomes besides mortality rates, Codman for the "end result idea" of evaluating the patient status one year after orthopaedic surgery, and Donabedian for taking Codman's work further and developing the structure-process-outcome model. The contribution of patient-centred outcome measurement is vast and paramount in education, audit and as an informative tool for healthcare professionals and decision makers. It is possible to collect these data nationwide which would then allow for cross country comparisons, as well as, economic evaluations in palliative care interventions to contribute to appropriate resource allocation.

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