Automorphisms of surfaces: Kummer rigidity and measure of maximal entropy

57 pages, 1 figureInternational audienceWe classify complex projective surfaces with an automorphism of positive entropy for which the unique invariant measure of maximal entropy is absolutely continuous with respect to Lebesgue measure

Influence of Local Mechanical Properties of High Strength Steel from Large Size Forged Ingot on Ultrasonic Wave Velocities

In the metallurgical industry, ultrasonic inspection is routinely used for the detection of defects. For the nondestructive inspection of small high strength steel parts, the material can be considered isotropic. However, when the size of the parts under inspection is large, the isotropic material hypothesis does not necessarily hold. The aim of this study is to investigate the effect of the variation in mechanical properties such as grain size, Young\u27s modulus, Poisson’s ratio, chemical composition on longitudinal and transversal ultrasonic wave velocities. A 2 cm thick slice cut from a 40-ton bainitic steel ingot that was forged and heat treated was divided into 875 parallelepiped samples of 2x4x7 cm3. A metallurgical study has been performed to identify the phase and measure the grain size. Ultrasonic velocity measurements at 2.25 MHz for longitudinal and transversal waves were performed. The original location of the parallelepiped samples in the large forged ingot and the measured velocities were used to produce an ultrasonic velocity map. Using a local isotropy assumption as well as the local density of the parallelepiped samples calculated from the chemical composition of the ingot provided by a previously published study [1], Young’s modulus and Poisson’s ratio were calculated from the longitudinal and transversal wave velocities. Microtensile measurements were used to validate Young’s modulus obtained by the ultrasonic wave velocity and an excellent match was observed

Une analyse des comportements de travailleurs masculins et féminins selon deux formes d'absence au travail

Les auteurs utilisent des données provenant d'entrevues afin de décrire les activités hors-travail d'un échantillon d'employés d'hôpital lors de journées passées à l'extérieur du travail.Even if the last fifty years of research is a testimony to its' importance to organizations, a satisfactory understanding of employee absence remains to be achieved. In reviewing the literature, this article shows that research on absence may be critiqued on two major grounds: a) A clear lack of mutual relationship between the empirical findings, the explanatory theories and the applied interventions, b) An over reliance on the absence record of employees as the dependent variable. It is further diagnosed that this problem may be directly attributed to the limitations in the basic paradygm used to study absence in organizations. Indeed, there has been practically no attempt to describe absence from the point of view of the absent person.This article attempts to contribute to the descriptive issue by presenting a complete re-analysis of a previously reported data set detailing how a sample of hospital workers spent their absence time.The data was gathered from 75 semi-skilled men and women employees who were interviewed immediately upon their return from a one day absence, which was either previously scheduled (day-off) or unplanned (absence). This data structuring presents the opportunity for investigating sex differences in absence time behaviors under two different types of absences. The raw interview information was subjected to content analyses by independent raters providing numerical structures which were then analysed quantitatively.The principal dependent variable was structured, using Robinson's (1977) classification scheme, around an «obligatory-leisure» continuum. Using this information structuring process and appropriate data transformation procedures it was possible to derive a single score for each respondent. This score expresses the total activity patterns during absence time in terms of the obligatory-leisure measure. The data was analysed using analyses of variance which were followed by hierarchical regressions. The initial analysis showed that women tend to engage in more obligatory activities during absences than their maie counterparts who maintained a greater equilibrium between leisure and obligatory activities (this accounting for 16% of the variance). There was a modest (p < .10) tendency for people to weight their activities towards leisure rather than obligatory activities during casual absence days. The hierarchical regressions showed that, in general, respondent sex was the single best predictor of absence time activities. This was particularly true for married (or cohabitating) women whose activities were clearly more obligatory. The marital status variable was a much better predictor of absence time activity structures than whether or not the respondent was responsable for dependents. For single people rather than gender it was age which best predicted how absence time was spent. However that equation showed low levels of prediction. The data was interpreted to indicate support for the generalized idea by which absences are generally taken for «purposive» reasons as opposed to respond to a desire for increased leisure time. This basic conclusion allows for an analysis of existing absence control programs in organizations. Other work has shown that absence control programs are indeed less powerful than might have once been thought. This data suggests a preliminary explanation: If absence is purposive the typical control of absence strategies (placing pressure on individuals, either by punishing absence or rewarding presence) will indeed yield sub optimal results. Consequently this report recommends the institution of absence control strategies which allow the employee greater flexibility in the distribution of time to meet work and non-work obligations.The paper presents an appraisal of this unusual procedure for the study of absence. It highlights the potential contributions as well as the inferential limits it forces upon both the practice and the theories of absence behavior. Suggestions for improvements in the research design close the paper

Les prédicteurs de la réussite dans l’enseignement supérieur

Ces trente dernières années, de nombreuses recherches en psychologie de l’éducation ont étudié les facteurs liés à la réussite dans l’enseignement supérieur. Cet article propose de réaliser une revue critique de la littérature sur ce sujet. Nous avons regroupé les différents prédicteurs qui ont été étudiés en quatre catégories : les caractéristiques d’entrée, l’environnement social, les croyances motivationnelles et l’engagement. Pour chaque catégorie, nous rendons compte des différents effets qui ont été observés dans des études anglo-saxonnes et européennes, identifions les résultats incohérents et soulignons les différentes limites que nous avons relevées. Cette analyse se termine par une discussion dans laquelle nous exposons les limites générales de cette littérature, nous proposons des implications pratiques de notre revue et des réflexions sur de nouvelles voies qui peuvent être empruntées dans cette étude. Notre objectif est de permettre au lecteur francophone d’acquérir une vision d’ensemble des principaux prédicteurs de la réussite dans l’enseignement supérieur.Over the last thirty years, countless research in educational psychology has studied factors related to achievement in higher education. This article presents a critical review of the literature on this topic. Various predictors have been put into four categories: background, social environment, motivational beliefs and student engagement. For each category, we shall report on the different effects that have been observed in Anglo-Saxon and European studies, identify inconsistent results and underline the various limits that we have identified. In the general discussion we shall outline the general limitations of studies conducted so far, suggest practical implications of reviewed findings as well as suggestions for future research. Our goal is to provide an overview of the main predictors of achievement in higher education to the French public

Financement des universités : pour un SYstème de répartition des Moyens à l\u27Activité et à la Performance (SYMPA) (le)

Sénat - Rapport d\u27information n° 382 (2007-2008) du 10 juin 2008 - par MM. Philippe ADNOT, Jean-Léonce DUPONT, Christian GAUDIN, Serge LAGAUCHE, Gérard LONGUET et Philippe RICHERT, fait au nom de la commission des Affaires culturelles et de la commission des Finances, du contrôle budgétaire et des comptes économiques de la Natio

Injury risk factors, screening tests and preventative strategies: A systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues

Purpose: To systematically review the scientific level of evidence for the ‘Top 3’ risk factors, screening tests and preventative exercises identified by a previously published survey of 44 premier league football (soccer) teams. Also, to provide an overall scientific level of evidence and graded recommendation based on the current research literature. Methods: A systematic literature search (Pubmed [MEDLINE], SportDiscus, PEDRO and Cochrane databases). The quality of the articles was assessed and a level of evidence (1++ to 4) was assigned. Level 1++ corresponded to the highest level of evidence available and 4, the lowest. A graded recommendation (A: strong, B: moderate, C: weak, D: insufficient evidence to assign a specific recommendation) for use in the practical setting was given. Results: Fourteen studies were analysed. The overall level of evidence for the risk factors previous injury, fatigue and muscle imbalance were 2++, 4 and ‘inconclusive’, respectively. The graded recommendation for functional movement screen, psychological questionnaire and isokinetic muscle testing were all ‘D’. Hamstring eccentric had a weak graded ‘C’ recommendation, and eccentric exercise for other body parts was ‘D’. Balance/proprioception exercise to reduce ankle and knee sprain injury was assigned a graded recommendation ‘D’. Conclusions: The majority of perceptions and practices of premier league teams have a low level of evidence and low graded recommendation. This does not imply that these perceptions and practices are not important or not valid, as it may simply be that they are yet to be sufficiently validated or refuted by research

Chronique d’une invention : le phonautographe d’Édouard-Léon Scott de Martinville (1817-1879) et les cercles parisiens de la science et de la technique

Cette étude, entreprise par la Commission d’histoire de la Société d’encouragement après la visite récente de chercheurs américains à la poursuite des grands ancêtres de l’enregistrement sonore, nous a conduits sur les traces d’un « artiste » peu connu aujourd’hui, Édouard-Léon Scott de Martinville [1817-1879]. L’activité de cet inventeur, précurseur des études modernes de phonétique acoustique, témoigne du fonctionnement des milieux académiques et industriels du Second Empire, à la charnière de la science et de la technique. Et ses apports se sont avérés aller bien au-delà de ce qu’il avait pu lui-même imaginer.Following a recent visit of two American scholars in Paris, looking for the great ancestors of the sound recordings, some members of the Historical Commission of the « Société d’encouragement pour l’industrie nationale » undertook a study on Edouard-Léon Scott de Martinville (1817-1879) and his activities. This inventor, who is not very well-known today, is one of the precursors of modern studies on acoustical phonetics. Scott’s activities illustrate the part played by academic and industrial circles during the French Second Empire for connecting between science and technology. Surprisingly, Scott’s contributions went beyond those he himself imagined

Epsilon toxin from C lostridium perfringens acts on oligodendrocytes without forming pores, and causes demyelination

International audienceEpsilon toxin (ET) is produced by Clostridium perfringens types B and D and causes severe neurological disorders in animals. ET has been observed binding to white matter, suggesting that it may target oligodendrocytes. In primary cultures containing oligodendrocytes and astrocytes, we found that ET (10(-9) M and 10(-7) M) binds to oligodendrocytes, but not to astrocytes. ET induces an increase in extracellular glutamate, and produces oscillations of intracellular Ca(2+) concentration in oligodendrocytes. These effects occurred without any change in the transmembrane resistance of oligodendrocytes, underlining that ET acts through a pore-independent mechanism. Pharmacological investigations revealed that the Ca(2+) oscillations are caused by the ET-induced rise in extracellular glutamate concentration. Indeed, the blockade of metabotropic glutamate receptors type 1 (mGluR1) prevented ET-induced Ca(2+) signals. Activation of the N-methyl-D-aspartate receptor (NMDA-R) is also involved, but to a lesser extent. Oligodendrocytes are responsible for myelinating neuronal axons. Using organotypic cultures of cerebellar slices, we found that ET induced the demyelination of Purkinje cell axons within 24 h. As this effect was suppressed by antagonizing mGluR1 and NMDA-R, demyelination is therefore caused by the initial ET-induced rise in extracellular glutamate concentration. This study reveals the novel possibility that ET can act on oligodendrocytes, thereby causing demyelination. Moreover, it suggests that for certain cell types such as oligodendrocytes, ET can act without forming pores, namely through the activation of an undefined receptor-mediated pathway

Epsilon toxin from Clostridium perfringens acts on oligodendrocytes without forming pores, and causes demyelination.

Epsilon toxin (ET) is produced by Clostridium perfringens types B and D and causes severe neurological disorders in animals. ET has been observed binding to white matter, suggesting that it may target oligodendrocytes. In primary cultures containing oligodendrocytes and astrocytes, we found that ET (10(-9) M and 10(-7) M) binds to oligodendrocytes, but not to astrocytes. ET induces an increase in extracellular glutamate, and produces oscillations of intracellular Ca(2+) concentration in oligodendrocytes. These effects occurred without any change in the transmembrane resistance of oligodendrocytes, underlining that ET acts through a pore-independent mechanism. Pharmacological investigations revealed that the Ca(2+) oscillations are caused by the ET-induced rise in extracellular glutamate concentration. Indeed, the blockade of metabotropic glutamate receptors type 1 (mGluR1) prevented ET-induced Ca(2+) signals. Activation of the N-methyl-D-aspartate receptor (NMDA-R) is also involved, but to a lesser extent. Oligodendrocytes are responsible for myelinating neuronal axons. Using organotypic cultures of cerebellar slices, we found that ET induced the demyelination of Purkinje cell axons within 24 h. As this effect was suppressed by antagonizing mGluR1 and NMDA-R, demyelination is therefore caused by the initial ET-induced rise in extracellular glutamate concentration. This study reveals the novel possibility that ET can act on oligodendrocytes, thereby causing demyelination. Moreover, it suggests that for certain cell types such as oligodendrocytes, ET can act without forming pores, namely through the activation of an undefined receptor-mediated pathway.journal articleresearch support, non-u.s. gov't2015 Mar2014 10 31importe