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Publicações

2015

Spatio-angular minimum-variance tomographic controller for multi-object adaptive-optics systems

Autores
Correia, CM; Jackson, K; Véran, JP; Andersen, D; Lardière, O; Bradley, C;

Publicação
Applied Optics

Abstract
Multi-object astronomical adaptive optics (MOAO) is now a mature wide-field observation mode to enlarge the adaptive-optics-corrected field in a few specific locations over tens of arcminutes. The work-scope provided by open-loop tomography and pupil conjugation is amenable to a spatio-angular linear-quadratic-Gaussian (SA-LQG) formulation aiming to provide enhanced correction across the field with improved performance over static reconstruction methods and less stringent computational complexity scaling laws. Starting from our previous work [J. Opt. Soc. Am. A 31, 101 (2014)], we use stochastic time-progression models coupled to approximate sparse measurement operators to outline a suitable SA-LQG formulation capable of delivering near optimal correction. Under the spatio-angular framework the wavefronts are never explicitly estimated in the volume, providing considerable computational savings on 10-m-class telescopes and beyond. We find that for Raven, a 10-m-class MOAO system with two science channels, the SA-LQG improves the limiting magnitude by two stellar magnitudes when both the Strehl ratio and the ensquared energy are used as figures of merit. The sky coverage is therefore improved by a factor of ~5. © 2015 Optical Society of America.

2015

The human transcriptome across tissues and individuals

Autores
Melé, M; Ferreira, PG; Reverter, F; DeLuca, DS; Monlong, J; Sammeth, M; Young, TR; Goldmann, JM; Pervouchine, DD; Sullivan, TJ; Johnson, R; Segrè, AV; Djebali, S; Niarchou, A; Wright, FA; Lappalainen, T; Calvo, M; Getz, G; Dermitzakis, ET; Ardlie, KG; Guigó, R;

Publicação
Science

Abstract
Transcriptional regulation and posttranscriptional processing underlie many cellular and organismal phenotypes. We used RNA sequence data generated by Genotype-Tissue Expression (GTEx) project to investigate the patterns of transcriptome variation across individuals and tissues. Tissues exhibit characteristic transcriptional signatures that show stability in postmortem samples. These signatures are dominated by a relatively small number of genes - which is most clearly seen in blood - though few are exclusive to a particular tissue and vary more across tissues than individuals. Genes exhibiting high interindividual expression variation include disease candidates associated with sex, ethnicity, and age. Primary transcription is the major driver of cellular specificity, with splicing playing mostly a complementary role; except for the brain, which exhibits a more divergent splicing program. Variation in splicing, despite its stochasticity, may play in contrast a comparatively greater role in defining individual phenotypes.

2015

Implantable Flexible Pressure Measurement System Based on Inductive Coupling

Autores
Oliveira, CC; Sepulveda, AT; Almeida, N; Wardle, BL; da Silva, JM; Rocha, LA;

Publicação
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING

Abstract
One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (EVAR). In spite of major advances in the operating techniques, complications still occur and lifelong surveillance is recommended. In order to reduce and even eliminate the commonly used surveillance imaging exams, as well as to reduce follow-up costs, new technological solutions are being pursued. In this paper, we describe the development, including design and performance characterization, of a flexible remote pressure measurement system based on inductive-coupling for post-EVAR monitoring purposes. The telemetry system architecture and operation are described and main performance characteristics discussed. The implantable sensor details are provided and its model is presented. Simulations with the reading circuit and the sensor's model were performed and compared with measurements carried out with air and a phantom as media, in order to characterize the telemetry system and validate the models. The transfer characteristic curve (pressure versus frequency) of the monitoring system was obtained with measurements performed with the sensor inside a controlled pressure vacuum chamber. Additional experimental results which proof the system functionality were obtained within a hydraulic test bench that emulates the aorta. Several innovative aspects, when compared to the state of the art, both in the sensor and in the telemetry system were achieved.

2015

Most Probable Explanation for MetaProbLog and Its Application in Heart Sound Segmentation

Autores
Mantadelis, T; Oliveira, J; Coimbra, MT;

Publicação
PLP@ICLP

Abstract
This paper, presents ongoing work that extends MetaProbLog with Most Probable Explanation (MPE) inference method. The MPE inference method is widely used in Hidden Markov Models in order to derive the most likely states of a model. Recently, we started developing an application that uses MetaProbLog to models phonocardiograms. We target to use this application in order to diagnose heart diseases by using phonocardiogram classification. Motivated by the importance of phonocardiogram classification, we started the implementation of the MPE inference method and an improvement of representation for annotated disjunctions.

2015

13th IEEE International Conference on Embedded and Ubiquitous Computing, EUC 2013, Porto, Portugal, October 21-23, 2015

Autores
Bozorgzadeh, E; Cardoso, JMP; Abreu, R; Memik, SO;

Publicação
EUC

Abstract

2015

Internationalisation of the firm theories: A schematic synthesis

Autores
Ribau, CP; Moreira, AC; Raposo, M;

Publicação
International Journal of Business and Globalisation

Abstract
This article carries out an integrative analysis of internationalisation theories. The most important contributions to the literature on internationalisation theories are used to create a schematic table giving a framework overview. This approach shows the high-level interaction of the literature, covering all internationalisation theories, their focus and basic assumptions, while at the same time showing their historical timeline. We identify the main schools of thought - ranging from economics based to integrative models - using an analysis that begins in the 18th century and ends in the 21st century with the most recent trends in internationalisation theories. This schematic and integrative analysis aims to support the academic community in their research on business internationalisation. Copyright © 2015 Inderscience Enterprises Ltd.

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