A new Algorithm Based on Factorization for Heterogeneous Domain Decomposition

Often computational models are too expensive to be solved in the entire domain of simulation, and a cheaper model would suffice away from the main zone of interest. We present for the concrete example of an evolution problem of advection reaction diffusion type a heterogeneous domain decomposition algorithm which allows us to recover a solution that is very close to the solution of the fully viscous problem, but solves only an inviscid problem in parts of the domain. Our new algorithm is based on the factorization of the underlying differential operator, and we therefore call it factorization algorithm. We give a detailed error analysis, and show that we can obtain approximations in the viscous region which are much closer to the viscous solution in the entire domain of simulation than approximations obtained by other heterogeneous domain decomposition algorithms from the literature.Comment: 23 page

Unsupervised Classification for Tiling Arrays: ChIP-chip and Transcriptome

Tiling arrays make possible a large scale exploration of the genome thanks to probes which cover the whole genome with very high density until 2 000 000 probes. Biological questions usually addressed are either the expression difference between two conditions or the detection of transcribed regions. In this work we propose to consider simultaneously both questions as an unsupervised classification problem by modeling the joint distribution of the two conditions. In contrast to previous methods, we account for all available information on the probes as well as biological knowledge like annotation and spatial dependence between probes. Since probes are not biologically relevant units we propose a classification rule for non-connected regions covered by several probes. Applications to transcriptomic and ChIP-chip data of Arabidopsis thaliana obtained with a NimbleGen tiling array highlight the importance of a precise modeling and the region classification

Family and Marriage: Institutions and the Need for Social Goods

Institutions, if unjust, ought to be reformed or even abolished. This radical Rawlsian thought leads to the question of whether the family ought to be abolished, given its negative impact on the very possibility of delivering equality of life chances. In this article, we address questions regarding the justice of the family, and of marriage, and reflect on rights, equality, and the provision of social goods by institutions. There is a temptation to justify our social institutions in terms which highlight their universal accessibility and benefits. But we may best understand the claim of some of our most important institutions where we recognize that they are forms of social good which may legitimately benefit some without having to benefit all. Their abolition is unjustified where there is sufficient value in them given our collective needs that it is unreasonable for some to refuse the means to maintain and promote these goods

Improvements on coronal hole detection in SDO/AIA images using supervised classification

We demonstrate the use of machine learning algorithms in combination with segmentation techniques in order to distinguish coronal holes and filaments in SDO/AIA EUV images of the Sun. Based on two coronal hole detection techniques (intensity-based thresholding, SPoCA), we prepared data sets of manually labeled coronal hole and filament channel regions present on the Sun during the time range 2011 - 2013. By mapping the extracted regions from EUV observations onto HMI line-of-sight magnetograms we also include their magnetic characteristics. We computed shape measures from the segmented binary maps as well as first order and second order texture statistics from the segmented regions in the EUV images and magnetograms. These attributes were used for data mining investigations to identify the most performant rule to differentiate between coronal holes and filament channels. We applied several classifiers, namely Support Vector Machine, Linear Support Vector Machine, Decision Tree, and Random Forest and found that all classification rules achieve good results in general, with linear SVM providing the best performances (with a true skill statistic of ~0.90). Additional information from magnetic field data systematically improves the performance across all four classifiers for the SPoCA detection. Since the calculation is inexpensive in computing time, this approach is well suited for applications on real-time data. This study demonstrates how a machine learning approach may help improve upon an unsupervised feature extraction method.Comment: in press for SWS

Réponses cardiorespiratoires lors d’épreuves d’effort pour les personnes utilisant un fauteuil roulant manuel : étude exploratoire chez les sujets sains

Travail d'intégration réalisé dans le cadre du cours PHT-6113.Introduction : L’avènement d’une lésion médullaire (LM) a un impact majeur au niveau de plusieurs systèmes dont le système cardiorespiratoire. Des protocoles d’évaluation standardisés pour mesurer la capacité aérobique existent, mais sont peu utilisés en physiothérapie pour une clientèle utilisatrice de fauteuil roulant manuel (FRM). Objectifs : Les objectifs principaux sont d’évaluer et de comparer les réponses cardiorespiratoires à différents tests d’effort chez des individus en bonne santé et de proposer des modifications à ces protocoles afin de sélectionner la ou les évaluation(s) optimale(s) pour une clientèle blessée médullaire utilisatrice de FRM. Méthodologie : Deux sujets sains ont complété cinq épreuves d’effort différentes à deux occasions à l’intérieur d’une période de sept jours. Deux tests d’effort sous-maximal et soutenu, soit le test de marche de six minutes (6MWT) et le test de propulsion manuelle de six minutes en fauteuil roulant (6WPT), et trois tests d’effort maximal et progressif, soit le protocole de Bruce (PB), l’ergomètre des membres supérieurs (EMS’s) et le fauteuil roulant sur tapis roulant (FRTR) ont été complétés. Les réponses cardiorespiratoires, incluant le VO2 et la fréquence cardiaque (FC), ont été mesurées à l’aide du Cosmed K4b2 et d’autres outils de mesure. Résultats : Le PB a généré le VO2 et la FC les plus élevés. L’EMS’s est celui ayant le VO2 de pointe le plus élevé comparativement au FRTR et au 6WPT. Finalement, les réponses cardiorespiratoires du 6WPT sont comparables à celles du 6MWT. Conclusion : À l’exception du VO2 de pointe, le 6WPT, l’EMS’s et le FRTR entraînent des réponses cardiorespiratoires similaires. Il est suggéré aux physiothérapeutes d’utiliser le 6WPT chez les individus ayant une LM puisqu’il est facilement reproductible et requiert peu d’équipements