Supercomputing futures : the next sharing paradigm for HPC resources : economic model, market analysis and consequences for the Grid

À la croisée des chemins du génie informatique, de la finance et de l'économétrie, cette thèse se veut fondamentalement un exercice en ingénierie économique dont l' objectif est de contribuer un système novateur, durable et adaptatif pour le partage de resources de calcul haute-performance. Empruntant à la finance fondamentale et à l'analyse technique, le modèle proposé construit des ratios et des indices de marché à partir de statistiques transactionnelles. Cette approche, encourageant les comportements stratégiques, pave la voie à une métaphore de partage plus efficace pour la Grid, où l'échange de ressources se voit maintenant pondéré. Le concept de monnaie de Grid, un instrument beaucoup plus liquide et utilisable que le troc de resources comme telles est proposé: les Grid Credits. Bien que les indices proposés ne doivent pas être considérés comme des indicateurs absolus et contraignants, ils permettent néanmoins aux négociants de se faire une idée de la valeur au marché des différentes resources avant de se positionner. Semblable sur de multiples facettes aux bourses de commodités, le Grid Exchange, tel que présenté, permet l'échange de resources via un mécanisme de double-encan. Néanmoins, comme les resources de super-calculateurs n'ont rien de standardisé, la plate-forme permet l'échange d'ensemble de commodités, appelés requirement sets, pour les clients, et component sets, pour les fournisseurs. Formellement, ce modèle économique n'est qu'une autre instance de la théorie des jeux non-coopératifs, qui atteint éventuellement ses points d'équilibre. Suivant les règles du "libre-marché", les utilisateurs sont encouragés à spéculer, achetant, ou vendant, à leur bon vouloir, l'utilisation des différentes composantes de superordinateurs. En fin de compte, ce nouveau paradigme de partage de resources pour la Grid dresse la table à une nouvelle économie et une foule de possibilités. Investissement et positionnement stratégique, courtiers, spéculateurs et même la couverture de risque technologique sont autant d'avenues qui s'ouvrent à l'horizon de la recherche dans le domaine

Spectral dimension reduction of complex dynamical networks

Dynamical networks are powerful tools for modeling a broad range of complex systems, including financial markets, brains, and ecosystems. They encode how the basic elements (nodes) of these systems interact altogether (via links) and evolve (nodes' dynamics). Despite substantial progress, little is known about why some subtle changes in the network structure, at the so-called critical points, can provoke drastic shifts in its dynamics. We tackle this challenging problem by introducing a method that reduces any network to a simplified low-dimensional version. It can then be used to describe the collective dynamics of the original system. This dimension reduction method relies on spectral graph theory and, more specifically, on the dominant eigenvalues and eigenvectors of the network adjacency matrix. Contrary to previous approaches, our method is able to predict the multiple activation of modular networks as well as the critical points of random networks with arbitrary degree distributions. Our results are of both fundamental and practical interest, as they offer a novel framework to relate the structure of networks to their dynamics and to study the resilience of complex systems.Comment: 16 pages, 8 figure

Economic impact of a heritage policy on residential property values in a historic district context : the case of the Old CIty of Québec

Previous studies have attempted to measure the willingness-to-pay to locate inside a historic district. Yet not enough attention has been paid to the implicit value attributed to the impact of heritage policies within the historic district. This paper fills that gap by investigating the impact of such policies on individual condominium properties for the case of the Old City of Quebec (Canada), designated by law as a protected area and included on the World Heritage List (UNESCO). More precisely, this research measures the impacts of the reorganization and landscaping of one particular street located south-west of the protection area in the old part of Quebec City. A difference-in-differences (DID) estimator based on a hedonic repeated sales approach is proposed to isolate such effects based on proximity to the site under study. Estimation results suggest that the reorganization of the street had no significant impact on the closest properties’ prices, but had negative effects for properties located within 150 to 450 meters of the street. These observations outline complex relations between heritage policies and urban landscaping projects

Interactions entre les professionnels d'une équipe de soins intensifs : les déterminants influençant la collaboration

Le travail d’équipe et la collaboration interprofessionnelle aux soins intensifs sont essentiels pour prodiguer des soins de qualité aux patients et pour leur sécurité. Cependant, les multiples interactions que nécessite une collaboration dans un contexte de soins aigus sont susceptibles de causer des tensions, des conflits et un travail inefficace dans l’équipe. Les déterminants de cette collaboration en soins intensifs ne sont pas encore bien identifiés. L'objectif de cette recherche est d'identifier et d'évaluer l’importance relative des déterminants susceptibles d’influencer la collaboration interprofessionnelle dans une équipe de soins intensifs. Un questionnaire évaluant ces déterminants a été élaboré et rempli par des professionnels de la santé travaillant dans quatre unités de soins intensifs d’un hôpital universitaire de Montréal. Un total de 312 professionnels, dont 46 médecins, 187 infirmières et 62 inhalothérapeutes, ont rempli le questionnaire. Des modèles d'analyses de régression multiple par hiérarchisation ont permis de déterminer que la « clarté du travail et des processus » , la « confiance et le respect » , mais tout particulièrement la « participation aux décisions » sont des déterminants statistiquement significatifs pour prédire la collaboration dans une équipe de soins intensifs. Une analyse de sous-groupe suggère des différences entre les médecins et les infirmières sur la perception de ces déterminants. Ces résultats apportent de nouveaux éléments dans la compréhension de la pratique de la collaboration et du travail d’équipe dans une équipe de soins intensifs, en précisant mieux ses déterminants. Sur le plan pratique, cela implique qu'il faille : i) favoriser un développement de la compétence de « collaboration » des professionnels travaillant dans le milieu des soins intensifs ; ii) cibler l’apprentissage auprès de ces professionnels en tenant compte des déterminants de la collaboration identifiés dans la présente étude.Teamwork and interprofessional collaboration in critical care are essentials to provide quality of care and patient safety. However, the multiple interactions that require collaboration in the context of acute care are likely to cause tensions, conflicts and inefficient team work. The determinants of this collaboration in critical care are not completely identified. The objective of this research is to identify and evaluate the relative importance of determinants that influence interprofessional collaboration in a critical care team. A survey assessing these determinants was developed and completed by healthcare professionals, working in four intensive care units of an university hospital in Montreal. A total of 312 professionals, including 46 physicians, 187 nurses and 62 respiratory therapists, completed the survey. Various models of multiple hierarchical regression analysis determined that "clarity of the work and processes", "trust and respect", and especially "participation in decisions" are statistically significant determinants which predict collaboration among the critical care team. Analysis of subgroup suggest differences between physicians and nurses perception of these determinants. These results provide new evidences to understand the process of collaboration and teamwork in a critical care team, through the clarification of its determinants. In practical terms, this means that we should : i) promote the development of "collaborative" competence among professionals working in the field of critical care ; ii) aim at teaching and educating the various professionals, taking into account the determinants of collaboration identified in this study

Behaviour of a double layer tensegrity grid under static loading: identification of self-stress level

International audienceThe determination of the state of internal stress is important to define the rigidity of a tensegrity structure and its stability. Severalmethods can be used; some are based on direct measurements of the forces in the elements, but are not easily transferable to a real structure.The authors opt for indirect measurement techniques, which seem more appropriate for implementation on-site. One can consider thevibratory anal-ysis of the elements, the vibratory analysis of the whole structure, or the analysis of the structure’s behavior under staticloading. Here, the node displacement fields of a tensegrity structure in different states of self-stress under several strategies of static loadingsis studied by comparing the measurement obtained by a tachometer with simulations. The aim of this work is to show the feasibility of adisplacement field to identify the state of self-stress by this analysis. It is shown that under certain conditions, plans can be made to replacethe direct measurement of the forces by indirect analysis

How does the timing of antiretroviral therapy initiation in acute infection affect HIV reservoirs?

The long-lived viral reservoir is a major obstacle to achieving a cure for HIV. Therapeutic strategies, such as early antiretroviral therapy (ART), may be a prerequisite to achieving long-term control of viral replication upon ART withdrawal

Caractéristiques dynamiques d'une structure de tenségrité en fonction de son niveau d'autocontrainte

Les structures de tenségrité sont des structures spatiales légères constituées de barres comprimées et de câbles tendus en état d'autocontrainte. L'autocontrainte assure la rigidité de la structure et sa stabilité. L'étude présente l'influence du niveau d'autocontrainte imposé au sein de la structure sur son comportement dynamique. Cette étude comporte une partie expérimentale sur une grille de tenségrité associée à la simulation numérique pour corréler la modélisation et les essais

Learning-by-Concordance (LbC): introducing undergraduate students to the complexity and uncertainty of clinical practice

Background: A current challenge in medical education is the steep exposure to the complexity and uncertainty of clinical practice in early clerkship. The gap between pre-clinical courses and the reality of clinical decision-making can be overwhelming for undergraduate students. The Learning-by-Concordance (LbC) approach aims to bridge this gap by embedding complexity and uncertainty by relying on real-life situations and exposure to expert reasoning processes to support learning. LbC provides three forms of support: 1) expert responses that students compare with their own, 2) expert explanations and 3) recognized scholars’ key-messages.Method: Three different LbC inspired learning tools were used by 900 undergraduate medical students in three courses: Concordance-of-Reasoning in a 1st-year hematology course; Concordance-of-Perception in a 2nd-year pulmonary physio-pathology course, and; Concordance-of-Professional-Judgment with 3rd-year clerkship students. Thematic analysis was conducted on freely volunteered qualitative comments provided by 404 students.Results:  Absence of a right answer was challenging for 1st year concordance-of-reasoning group; the 2nd year visual concordance group found radiology images initially difficult and unnerving and the 3rd year concordance-of-judgment group recognized the importance of divergent expert opinion.Conclusions: Expert panel answers and explanations constitute an example of “cognitive apprenticeship” that could contribute to the development of appropriate professional reasoning processes

An instrument to measure psychosocial determinants of health care professionals’ vaccination behavior:Validation of the Pro-VC-Be questionnaire

International audienc

Subsequent Event Risk in Individuals with Established Coronary Heart Disease:Design and Rationale of the GENIUS-CHD Consortium

BACKGROUND: The "GENetIcs of sUbSequent Coronary Heart Disease" (GENIUS-CHD) consortium was established to facilitate discovery and validation of genetic variants and biomarkers for risk of subsequent CHD events, in individuals with established CHD. METHODS: The consortium currently includes 57 studies from 18 countries, recruiting 185,614 participants with either acute coronary syndrome, stable CHD or a mixture of both at baseline. All studies collected biological samples and followed-up study participants prospectively for subsequent events. RESULTS: Enrollment into the individual studies took place between 1985 to present day with duration of follow up ranging from 9 months to 15 years. Within each study, participants with CHD are predominantly of self-reported European descent (38%-100%), mostly male (44%-91%) with mean ages at recruitment ranging from 40 to 75 years. Initial feasibility analyses, using a federated analysis approach, yielded expected associations between age (HR 1.15 95% CI 1.14-1.16) per 5-year increase, male sex (HR 1.17, 95% CI 1.13-1.21) and smoking (HR 1.43, 95% CI 1.35-1.51) with risk of subsequent CHD death or myocardial infarction, and differing associations with other individual and composite cardiovascular endpoints. CONCLUSIONS: GENIUS-CHD is a global collaboration seeking to elucidate genetic and non-genetic determinants of subsequent event risk in individuals with established CHD, in order to improve residual risk prediction and identify novel drug targets for secondary prevention. Initial analyses demonstrate the feasibility and reliability of a federated analysis approach. The consortium now plans to initiate and test novel hypotheses as well as supporting replication and validation analyses for other investigators