r-matrices for relativistic deformations of integrable systems

We include the relativistic lattice KP hierarchy, introduced by Gibbons and Kupershmidt, into the $r$-matrix framework. An $r$-matrix account of the nonrelativistic lattice KP hierarchy is also provided for the reader's convenience. All relativistic constructions are regular one-parameter perturbations of the nonrelativistic ones. We derive in a simple way the linear Hamiltonian structure of the relativistic lattice KP, and find for the first time its quadratic Hamiltonian structure. Amasingly, the latter turns out to coincide with its nonrelativistic counterpart (a phenomenon, known previously only for the simplest case of the relativistic Toda lattice)

La sexualité à l’ère numérique : les adolescents et le sexting

Bien que la recherche commence à s’intéresser au sexting par rapport aux taux de prévalence et que des campagnes de prévention aient été créées pour cette problématique, des recherches plus approfondies sont nécessaires afin de comprendre tous les enjeux entourant la pratique chez les jeunes, particulièrement lorsqu’elle entraine des conséquences négatives. Nos questions de recherche sont les suivantes : Quelles sont les différents éléments qui définissent le sexting du point de vue des jeunes, des parents et des enseignants ? Quelle est la définition du sexting ? Quelles sont les raisons qui peuvent motiver une personne à pratiquer le sexting (en termes d’envoi et de réception) mais aussi à transférer le contenu à d’autres personnes ? Quels sont les risques, conséquences et réactions possibles, notamment en termes de jugement ? Est-ce que la prévention relative au sexting est utile ? Que pourrait-on faire pour prévenir

Rapport final de l'étude longitudinale [email protected]

En Suisse, à l'instar de ce que l'on constate dans d'autres pays d'Europe, le pourcentage des 14 à 19 ans utilisant régulièrement Internet a augmenté de manière spectaculaire entre 1997 (4%) et 2013 (97%) selon les chiffres de l'Office fédéral de la statistique. De par sa commodité d'accès en tout lieu et en tout temps, les jeunes ont su s'approprier les usages et les activités variées d'Internet et ils y passent une partie importante de leur temps pour se divertir, s'informer ou étudier. A ce jour, rares sont encore les études longitudinales qui permettent d'examiner l'évolution de leurs usages d'internet ou les implications à moyen et long terme de ce média sur la santé des adolescents. Pratiques en constante mutation, il est impératif de suivre l'évolution d'Internet des adolescents, car ces derniers constituent un groupe particulièrement vulnérable aux multiples attractions du web. Objectifs : Les objectifs principaux de cette étude étaient de: 1. Quantifier l'évolution sur les deux ans de l'utilisation d'Internet chez les adolescents vaudois en faisant la distinction entre le temps dédié à l'école/au travail et le temps dédié aux loisirs ; 2. Décrire les activités en ligne qui occupent les adolescents et investiguer si ces activités changent au fil du temps

Correlates of extracurricular sport participation among Swiss adolescents

Background: Based on a large national survey on the health of adolescents, this paper focuses on the socio-demographic and lifestyle correlates of sport practice among Swiss adolescents. The SMASH2002 database includes 7428 vocational apprentices and high school students between the ages of 16 and 20 who answered a self-administered anonymous questionnaire containing 565 items targeting perceived health, health attitudes and behaviour. Weekly episodes of extracurricular sport activity were measured by a four-category scale, and the sample was dichotomised between active (≥two episodes of sport/week) and inactive (<two episodes of sport/week) respondents. Thirty percent of female respondents and 40.2% of male respondents reported engaging in sport activity at least two to three times a week; another 9.7% of the female and 19.4% of the male respondents reported participating in least one sport activity each day (p<0.01). The percentage of active respondents was higher among students than among vocational apprentices (p<.01), and the rates of sport activity decreased more sharply over time among the apprentices than among the students (p<0.01). Most active adolescents reported having a better feeling of well-being than their inactive peers [among male students: odds ratio (OR): 3.13; 95% confidence interval (95%CI): 1.28-7.70]. The percentage of active females who reported being on a diet was high, and female apprentices exhibited higher involvement in dieting than their inactive peers (OR: 1.68; 95%CI: 1.32-2.14). Relative to the inactive male respondents, the proportion of active male respondents smoking was lower; however, a lower proportion of the latter group did not report drunkenness, and the percentage of those who reported lifetime cannabis consumption was higher among active than inactive students (females, OR:1.57; 95%CI:1.09-2.25; males, OR:1.80; 95%CI: 20-2.69). Conclusion: Organised sport activities should be better tailored to the work schedules of apprentices. Practitioners should be aware of the potential for problematic behaviour in the area of dieting and substance use among a subset of sport-oriented adolescent

Screening for cardiovascular disease risk factors beginning in childhood

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Individual detection and intervention on CVD risk factors and behaviors throughout childhood and adolescence has been advocated as a strategy to reduce CVD risk in adulthood. The U.S. National Heart, Lung, and Blood Institute (NHLBI) has recently recommended universal screening of several risk factors in children and adolescents, at odds with several recommendations of the U.S. Services Task Force and of the U.K. National Screening committee. In the current review, we discuss the goals of screening for CVD risk factors (elevated blood pressure, abnormal blood lipids, diabetes) and behaviors (smoking) in children and appraise critically various screening recommendations. Our review suggests that there is no compelling evidence to recommend universal screening for elevated blood pressure, abnormal blood lipids, abnormal blood glucose, or smoking in children and adolescents. Targeted screening of these risk factors could be useful but specific screening strategies have to be evaluated. Research is needed to identify target populations, screening frequency, intervention, and follow-up. Meanwhile, efforts should rather focus on the primordial prevention of CVD risk factors and at maintaining a lifelong ideal cardiovascular health through environmental, policy, and educational approaches

Screening for cardiovascular disease risk factors beginning in childhood

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Individual detection and intervention on CVD risk factors and behaviors throughout childhood and adolescence has been advocated as a strategy to reduce CVD risk in adulthood. The U.S. National Heart, Lung, and Blood Institute (NHLBI) has recently recommended universal screening of several risk factors in children and adolescents, at odds with several recommendations of the U.S. Services Task Force and of the U.K. National Screening committee. In the current review, we discuss the goals of screening for CVD risk factors (elevated blood pressure, abnormal blood lipids, diabetes) and behaviors (smoking) in children and appraise critically various screening recommendations. Our review suggests that there is no compelling evidence to recommend universal screening for elevated blood pressure, abnormal blood lipids, abnormal blood glucose, or smoking in children and adolescents. Targeted screening of these risk factors could be useful but specific screening strategies have to be evaluated. Research is needed to identify target populations, screening frequency, intervention, and follow-up. Meanwhile, efforts should rather focus on the primordial prevention of CVD risk factors and at maintaining a lifelong ideal cardiovascular health through environmental, policy, and educational approaches

Femtosecond study of the interplay between excitons, trions, and carriers in (Cd,Mn)Te quantum wells

We present an absorption study of the neutral and positively charged exciton (trion) under the influence of a femtosecond, circularly polarized, resonant pump pulse. Three populations are involved: free holes, excitons, and trions, all exhibiting transient spin polarization. In particular, a polarization of the hole gas is created by the formation of trions. The evolution of these populations is studied, including the spin flip and trion formation processes. The contributions of several mechanisms to intensity changes are evaluated, including phase space filling and spin-dependent screening. We propose a new explanation of the oscillator strength stealing phenomena observed in p-doped quantum wells, based on the screening of neutral excitons by charge carriers. We have also found that binding heavy holes into charged excitons excludes them from the interaction with the rest of the system, so that oscillator strength stealing is partially blockedComment: 4 pages, 4 figure

La sexualité à l’ère numérique : les adolescents et le sexting 2.0, 2ème phase

Le sexting a d’abord été rendu public par des cas dramatiques relayés par la presse dans lesquels des jeunes filles avaient été harcelées à la suite de la publication et du partage d’une de leurs photos intimes. Pourtant, depuis, cette pratique a également été appréhendée de manière plus positive ou moins alarmiste, pouvant raisonnablement faire partie du développement et des expérimentations des jeunes. En 2016, nous avons mené une première recherche qualitative qui avait pour but d’explorer la pratique du sexting chez les jeunes en menant des groupes focus avec des jeunes âgés de 16 à 21 ans, des parents et des enseignants d’enfants et d’élèves âgés d’au moins 11 ans. Dans le cadre de cette première étude, certains résultats nous ont amené à élaborer une étape exploratoire supplémentaire. Ainsi, nous avons souhaité continuer notre approche exploratoire de la pratique du sexting en incluant les opinions et interprétations des jeunes âgés de 12 à 15 ans ou en tout cas encore dans le système d’école obligatoire. Ajouter les opinions et interprétations des 12-15 ans nous offrira une vision complète de la problématique du sexting et permettra assurément d’adapter les messages de prévention au plus près de la pratique en établissant les différents facteurs de risque et de protection quant à la pratique du sexting. Cette recherche peut être considérée comme la suite de la première recherche menée en 2016 auprès des jeunes âgées de 16 à 21 ans, des enseignants et des parents. Ainsi, les objectifs et les méthodes sont très similaires

Additional Constants of Motion for a Discretization of the Calogero--Moser Model

The maximal super-integrability of a discretization of the Calogero--Moser model introduced by Nijhoff and Pang is presented. An explicit formula for the additional constants of motion is given.Comment: 7 pages, no figure

Functional representation of the Ablowitz-Ladik hierarchy. II

In this paper I continue studies of the functional representation of the Ablowitz-Ladik hierarchy (ALH). Using formal series solutions of the zero-curvature condition I rederive the functional equations for the tau-functions of the ALH and obtain some new equations which provide more straightforward description of the ALH and which were absent in the previous paper. These results are used to establish relations between the ALH and the discrete-time nonlinear Schrodinger equations, to deduce the superposition formulae (Fay's identities) for the tau-functions of the hierarchy and to obtain some new results related to the Lax representation of the ALH and its conservation laws. Using the previously found connections between the ALH and other integrable systems I derive functional equations which are equivalent to the AKNS, derivative nonlinear Schrodinger and Davey-Stewartson hierarchies.Comment: arxiv version is already officia