Tight Bounds for Asymptotic and Approximate Consensus

We study the performance of asymptotic and approximate consensus algorithms under harsh environmental conditions. The asymptotic consensus problem requires a set of agents to repeatedly set their outputs such that the outputs converge to a common value within the convex hull of initial values. This problem, and the related approximate consensus problem, are fundamental building blocks in distributed systems where exact consensus among agents is not required or possible, e.g., man-made distributed control systems, and have applications in the analysis of natural distributed systems, such as flocking and opinion dynamics. We prove tight lower bounds on the contraction rates of asymptotic consensus algorithms in dynamic networks, from which we deduce bounds on the time complexity of approximate consensus algorithms. In particular, the obtained bounds show optimality of asymptotic and approximate consensus algorithms presented in [Charron-Bost et al., ICALP'16] for certain dynamic networks, including the weakest dynamic network model in which asymptotic and approximate consensus are solvable. As a corollary we also obtain asymptotically tight bounds for asymptotic consensus in the classical asynchronous model with crashes. Central to our lower bound proofs is an extended notion of valency, the set of reachable limits of an asymptotic consensus algorithm starting from a given configuration. We further relate topological properties of valencies to the solvability of exact consensus, shedding some light on the relation of these three fundamental problems in dynamic networks

Le diagnostic des tuméfactions latérales solides cervicales chez l'enfant

Introduction : Faute de tests diagnostiques précis, une étude histologique est souvent nécessaire pour diagnostiquer les tuméfactions latérales solides cervicales (TLSC) chez l’enfant. Nous étudierons les modalités diagnostiques pour les TLSC afin de créer une approche diagnostique standardisée intégrant de nouveaux outils diagnostics à ceux actuellement offerts. Méthodologie : Après révision des étiologies et des modalités diagnostiques, une revue de la littérature a été effectuée. Une étude rétrospective entre 2002 à 2012 est présentée suivie d’une étude de faisabilité de la cytoponction. Puis, un arbre décisionnel est créé basé sur nos résultats et sur l’avis d’un groupe d’experts de différentes disciplines médicales. Résultats : Le diagnostic différentiel des TLSC est varié, la littérature scientifique est désuète et la comparaison reste difficile. Pour nos 42 enfants avec un âge médian de sept ans, les tuméfactions inflammatoires représentent 59% (26/44 biopsies) des TLSC, surtout des lymphadénites à mycobactérie atypique (13/26) qui ont un dépistage ardu et multimodal. La biopsie fut peu contributive à la prise en charge dans 39% (17/44) des cas. La cytoponction sous échoguidance est une technique diagnostique faisable et moins invasive que la biopsie. L’arbre décisionnel offre aux cliniciens une approche diagnostique standardisée des TLSC appuyée sur des faits scientifiques que nous souhaitons valider par une étude prospective. Conclusion : Les TLSC chez l’enfant représentent un défi diagnostic et notre arbre décisionnel répond au manque de standardisation dans l’approche diagnostique. Une étude prospective sur notre arbre décisionnel est en voie d’acceptation au CHU Sainte-Justine.Introduction: Histological studies are often required to establish the etiology of solid lateral cervical masses (SLCM) in children since diagnostic tools are lacking accuracy. We evaluated the diagnostic tools available in order to develop a systematic and standardized diagnostic approach. Methods: After etiologies and diagnostic tools were described, a review of the scientific literature on the topic was performed. A retrospective study between 2002 and 2012 of SLCM was conducted. A case report showing the feasibility of Fine Needle Aspiration (FNA) is presented. Finally, a decision algorithm integrating our results and the scientific opinion of an expert group is proposed. Results: Differential diagnosis for SLCM is wide. The scientific literature regarding their diagnosis is weak, outdated and comparison is difficult. The 42 children studied had a median age of seven year old. They had inflammatory masses in 59% (26/44 biopsies) with mostly Atypical Mycobacteria (13/26), which has been shown to be difficult to confirm and often requires multiple diagnostic tests. The benefit of biopsy is questionable in 39% (17/44) of biopsies. Ultrasound-guided FNA appears to be a feasible technique and less invasive than biopsy. The algorithm proposes a standardized approach based on scientific facts that we want to evaluate through a prospective study. Conclusion: SLCM in children represent a diagnostic challenge and the algorithm intends to guide the clinician’s diagnostic approach. A prospective study on the algorithm created is at its final step for acceptance through the CHU Sainte-Justine authorities

L’expérience subjective de la psychose : récits et trajectoires de jeunes d’Auberges du coeur

La conceptualisation du phénomène de psychose et les façons de s’en «rétablir» sont fortement influencées par le modèle biomédical. Or, d’autres perspectives existent et sont pertinentes pour développer une compréhension plus aiguisée et critique de l’expérience de la psychose. On peut notamment penser à la phénoménologie, les approches basées sur le savoir expérientiel et les approches alternatives en santé mentale. Afin d’explorer un phénomène peu étudié empiriquement et d’offrir un espace de parole à des personnes marginalisées, ce mémoire illustre qu’une pluralité de discours et d’approches relativement à la psychose existe, mais que peu d’espace est accordé à la subjectivité et à la souffrance. La question guidant la démarche est la suivante : Quel sens et quelles significations les jeunes adultes hébergés en Auberge du coeur et ayant un suivi dans une clinique Premier épisode psychotique (PEP) donnent-ils à l’expérience de la psychose? À cet égard, quelle est la place de différents discours sur la psychose dans leurs récits? Une démarche qualitative a été privilégiée pour mener cette démarche. Six jeunes adultes ayant vécu une expérience de psychose ainsi qu’une expérience d’itinérance ont été rencontrés. Les entrevues s’intéressaient au parcours des jeunes, à leurs visions du monde et à leurs perceptions de différents services reçus durant leur parcours. Adoptant un cadre conceptuel fluide et pluriel, différentes perspectives ont été utilisées pour analyser les résultats. Entre autres, des écrits s’intéressant à la subjectivité et aux expériences ont été utilisés, ainsi que ceux s’intéressant à la conceptualisation de la souffrance. Les analyses ont mis en lumière que les parcours des jeunes sont caractérisés par de l’adversité et des traumas, ainsi que de détresse psychologique. Également, leurs récits illustrent que la psychose est une expérience difficile à saisir et verbaliser. Le réductionnisme de l’approche biomédicale est fort, et cela se traduit notamment par une difficulté à offrir des espaces pour accueillir la souffrance des jeunes relativement à leurs expériences de psychose.The conception of psychosis and its recovery are mostly influenced by biomedical models of mental illness. Other perspectives exist and are useful to understand the experience of psychosis, in a more global and critique way. The phenomenology, the experiential approach and alternative approaches are interesting and useful to increase our knowledge on psychosis experience. This project has the purpose to explore a phenomenon which is not so known in the research community, as well as giving a space to young adults to talk about their experience of psychosis. We found that even though many approaches are interested in the experience of psychosis, there are not so many spaces to talk about the suffering that comes with that experience. The question that guided the research was: What is the meaning and the significations of psychosis for young adults that were living in an Auberge du Coeur, and receiving services from a Premier Épisode Psychotique (PEP) clinic? Also, what approaches of psychosis are part of their storytelling? To answer this question, a qualitative methodology was used. Six young adults that had experienced a psychosis and had been homeless were interviewed. We were interested in their lifepath, their vision of the world and their perception of different services they were in touch with. Many perspectives were developed so that the data analysis can be critique. We were interested in the concept of subjectivity, the knowledge about experiences and the concept of suffering. The analysis shown that all the participants experienced a lot of difficulties beside the psychosis experience, such as traumas and psychological distress. We also found that the psychosis experience is hard to get and hard to reach for them. It is especially hard to explain how it feels with words. In their storytelling, we see that the biomedical models are predominant. It seems like the participants were not able to find spaces to talk about the suffering that comes with psychosis experience, even though they receive help from community centers and public services

Topographical coloured plasmonic coins

The use of metal nanostructures for colourization has attracted a great deal of interest with the recent developments in plasmonics. However, the current top-down colourization methods based on plasmonic concepts are tedious and time consuming, and thus unviable for large-scale industrial applications. Here we show a bottom-up approach where, upon picosecond laser exposure, a full colour palette independent of viewing angle can be created on noble metals. We show that colours are related to a single laser processing parameter, the total accumulated fluence, which makes this process suitable for high throughput industrial applications. Statistical image analyses of the laser irradiated surfaces reveal various distributions of nanoparticle sizes which control colour. Quantitative comparisons between experiments and large-scale finite-difference time-domain computations, demonstrate that colours are produced by selective absorption phenomena in heterogeneous nanoclusters. Plasmonic cluster resonances are thus found to play the key role in colour formation.Comment: 9 pages, 5 figure

Physiological Responses to Repeated Running Sprint Ability Tests: A Systematic Review

International Journal of Exercise Science 13(4): 1190-1205, 2020. The purpose of this study was to review acute physiological responses induced by repeated running sprint ability (RRSA) tests that could serve as references for practitioners utilising repeated sprints as a performance measure with athletes. This research was conducted following the PRISMA methodology. The systematic search was conducted in November 2019 and yielded 26 different scientific articles. Only peer-reviewed full-text article were included as abstracts are too short to allow proper explanation of the RRSAT methodology that was employed. According to the present literature, practitioners should use the following assessments: the 6x40m RRSA protocol with one Change of Direction (COD) (20+20 m with a 180° COD) and 25s of passive recovery between sprints with soccer players; the Intensive Repeated Sprint Ability (IRSA) test with men basketball players; the Futsal Intermittent Endurance Test (FIET) with futsal players; the Repeated Shuttle Sprint Test (RSST) with men handball players; and the Multiple Repeated Sprint Ability test for Badminton players (MRSAB). The present review should serve as a reference standard for RRSA tests. Further research should be directed towards creating and validating more specific RRSA tests protocols to each sports physiological and physical demands

Body Composition (DXA) and Maximal Strength of Powerlifters: a Descriptive Quantitative and Longitudinal Study

International Journal of Exercise Science 16(4): 828-845, 2023. The purpose of this study was to present the relationships between maximal strength and body composition and to conduct yearly follow-ups presenting the chronic effects of maximal strength training on body composition. Thirty-four (age = 28.8 ± 8.7 yrs) classic powerlifters (M = 21; F = 13) completed at least one Dual-Energy X-Ray Absorptiometry (DXA) 43.97 ± 23.93 days after a sanctioned international powerlifting federation affiliate competition (Squat + Bench Press + Deadlift = Total (kg)). In addition, thirteen subjects (n = 13) completed at least one yearly follow up. Paired sample T-Tests and simple linear regressions were performed to determine significant effects on body composition and maximal strength measures. Prediction formulas were obtained as follows: Bone Mineral Content (BMC) (g) = 3.39 * Total (kg) + 1494.78 (r = 0.84; p \u3c 0.000; SEE = 348.05); Bone Mineral Density (BMD) (g/cm3) = 0.000390 * Total (kg) + 1.115 (r = 0.71; p \u3c 0.000; SEE = 0.062); Total (kg) = 10.84 * Lean Body Weight (LBW) (kg) – 154.89 (r = 0.90; p \u3c 0.000; SEE = 70.27); Total (kg) = 22.74 * Relative LBW (kg/m) – 306.66 (r = 0.92; p \u3c 0.000; SEE = 64.07). Significant differences were observed in BMD (+1.57 ± 1.55%; p = 0.018; ES = 0.22), between measures one and two (333.7 ± 36.3 days apart) as well as LBW (-2.95 ± 3.82%; p = 0.049; ES = 0.16), and Body Fat Percentage (+2.59%; p = 0.029; ES = 0.20) between measures two and three (336 ± 13.3 days apart). Thus, maximal strength can be used to predict BMC and BMD, while LBW can be used to predict maximal strength. As well, consistent powerlifting practice can increase BMD in adults

Flood frequency analysis at ungauged catchments with the GAM and MARS approaches in the Montreal region, Canada

Regional frequency analysis (RFA) aims to estimate quantiles of extreme hydrological variables (e.g. floods or low-flows) at sites where little or no hydrological data is available. This information is of interest for the optimal planning and management of water resources. A number of regional estimation models are evaluated and compared in this study and then used for regional estimation of flood quantiles at ungauged catchments located in the Montreal region in southern Quebec, Canada. In this study, two neighborhood approaches using canonical correlation analysis (CCA) and the region of influence (ROI) method are applied to delineate homogenous regions. Three regression methods namely log-linear regression model (LLRM), generalized additive models (GAM), and multivariate adaptive regression splines (MARS), recently introduced in the RFA context, are considered for regional estimation. These models are also applied considering all stations (ALL). The considered models, especially MARS, have never been used previously in a concrete application. Results indicate that MARS and GAM have comparable predictive performances, especially when applied with the whole dataset. Results also show that MARS used in combination with the CCA approach provide improved performances compared to all considered regional approaches. This may reflect the flexibility of the combination of these two approaches, their robustness, and their ability to better reproduce the hydrological phenomena, especially in real-world conditions when limited data are available