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Publicações

2014

Segmentation of the vascular network of the Retina

Autores
Mendonça A.M.; Dashtbozorg B.; Campilho A.;

Publicação
Image Analysis and Modeling in Ophthalmology

Abstract
The retina is a unique region where the vascular condition can be observed in vivo. It is a window to the systemic vasculature, as the retinal blood vessels are exposed to the same stresses and pathologies as the whole vascular system. The retinal vasculature status can be evaluated with high-resolution eye fundus color images, and variations in the retinal microcirculation can be used as an indicator of a lesion in the cerebral microvasculature. The features measured on these images can characterize retinal arteriolar narrowing, which is a marker of hypertension, or diabetic retinopathy (DR).

2014

Improving Branch-and-Price for Parallel Machine Scheduling

Autores
Lopes, M; Alvelos, F; Lopes, H;

Publicação
COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2014, PT II

Abstract
In this paper we present a hybrid exact-heuristic method to improve a branch-and-price algorithm to solve the unrelated parallel machines with sequence-dependent setup times scheduling problem. As most of the computational time in the column generation (CG) process is spent in subproblems, two new heuristics to solve the subproblems are embedded in the branch-and-price (BP) framework with the aim to improve the efficiency of the process in obtaining optimal solutions. Computational results show that the proposed method improves a state-of-the-art BP algorithm from the literature, providing optimal solutions for large instances (e. g. 50 machines and 180 jobs) of the parallel machine scheduling problem with sequence dependent setup times, in significantly less time. One of the proposed approaches reduces, in average, to a half the time spent in the root of the branch-and-price tree and to a quarter the time spent in the full branch-and-price algorithm.

2014

Distributed Adaptive Model Rules for Mining Big Data Streams

Autores
Vu, AT; Morales, GD; Gama, J; Bifet, A;

Publicação
2014 IEEE INTERNATIONAL CONFERENCE ON BIG DATA (BIG DATA)

Abstract
Decision rules are among the most expressive data mining models. We propose the first distributed streaming algorithm to learn decision rules for regression tasks. The algorithm is available in SAMOA (SCALABLE ADVANCED MASSIVE ONLINE ANALYSIS), an open-source platform for mining big data streams. It uses a hybrid of vertical and horizontal parallelism to distribute Adaptive Model Rules (AMRules) on a cluster. The decision rules built by AMRules are comprehensible models, where the antecedent of a rule is a conjunction of conditions on the attribute values, and the consequent is a linear combination of the attributes. Our evaluation shows that this implementation is scalable in relation to CPU and memory consumption. On a small commodity Samza cluster of 9 nodes, it can handle a rate of more than 3 0 0 0 0 instances per second, and achieve a speedup of up to 4.7 x over the sequential version.

2014

Transcriptome characterization by RNA sequencing identifies a major molecular and clinical subdivision in chronic lymphocytic leukemia

Autores
Ferreira, PG; Jares, P; Rico, D; Gómez López, G; Martínez Trillos, A; Villamor, N; Ecker, S; González Pérez, A; Knowles, DG; Monlong, J; Johnson, R; Quesada, V; Djebali, S; Papasaikas, P; López Guerra, M; Colomer, D; Royo, C; Cazorla, M; Pinyol, M; Clot, G; Aymerich, M; Rozman, M; Kulis, M; Tamborero, D; Gouin, A; Blanc, J; Gut, M; Gut, I; Puente, XS; Pisano, DG; Martin Subero, JI; López Bigas, N; López Guillermo, A; Valencia, A; López Otín, C; Campo, E; Guigó, R;

Publicação
Genome Research

Abstract
Chronic lymphocytic leukemia (CLL) has heterogeneous clinical and biological behavior. Whole-genome and -exome sequencing has contributed to the characterization of the mutational spectrum of the disease, but the underlying transcriptional profile is still poorly understood. We have performed deep RNA sequencing in different subpopulations of normal B-lymphocytes and CLL cells from a cohort of 98 patients, and characterized the CLL transcriptional landscape with unprecedented resolution. We detected thousands of transcriptional elements differentially expressed between the CLL and normal B cells, including protein-coding genes, noncoding RNAs, and pseudogenes. Transposable elements are globally derepressed in CLL cells. In addition, two thousand genes-most of which are not differentially expressed-exhibit CLL-specific splicing patterns. Genes involved in metabolic pathways showed higher expression in CLL, while genes related to spliceosome, proteasome, and ribosome were among the most down-regulated in CLL. Clustering of the CLL samples according to RNA-seq derived gene expression levels unveiled two robust molecular subgroups, C1 and C2. C1/C2 subgroups and the mutational status of the immunoglobulin heavy variable (IGHV ) region were the only independent variables in predicting time to treatment in a multivariate analysis with main clinico-biological features. This subdivision was validated in an independent cohort of patients monitored through DNA microarrays. Further analysis shows that B-cell receptor (BCR) activation in the microenvironment of the lymph node may be at the origin of the C1/C2 differences. © 2014 Hansen et al.

2014

Analysis of electricity market prices using multidimensional scaling

Autores
Azevedo, F; Machado, JT;

Publicação
Mathematical Methods in Engineering

Abstract
This paper studies the impact of the energy upon electricity markets using Multidimensional Scaling (MDS). Data from major energy and electricity markets is considered. Several maps produced by MDS are presented and discussed revealing that this method is useful for understanding the correlation between them. Furthermore, theresults help electricity markets agents hedging against Market Clearing Price (MCP) volatility. © Springer Science+Business Media Dordrecht 2014.

2014

BHP universality in energy sources

Autores
Ferreira, H; Goncalves, R; Pinto, AA;

Publicação
Springer Proceedings in Mathematics and Statistics

Abstract

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