The GRB luminosity function in the internal shock model confronted to observations

We compute the expected luminosity function of GRBs in the context of the internal shock model. We assume that GRB central engines generate relativistic outflows characterized by the respective distributions of injected kinetic power Edot and contrast in Lorentz factor Kappa = Gamma_max/Gamma_min. We find that if the distribution of contrast extends down to values close to unity (i.e. if both highly variable and smooth outflows can exist) the luminosity function has two branches. At high luminosity it follows the distribution of Edot while at low luminosity it is close to a power law of slope -0.5. We then examine if existing data can constrain the luminosity function. Using the log N - log P curve, the Ep distribution of bright BATSE bursts and the XRF/GRB ratio obtained by HETE2 we show that single and broken power-laws can provide equally good fits of these data. Present observations are therefore unable to favor one form of the other. However when a broken power-law is adopted they clearly indicate a low luminosity slope ~ -0.6 +- 0.2, compatible with the prediction of the internal shock model.Comment: 9 pages, 5 figure

The Athlete's Heart in Adolescent Africans An Electrocardiographic and Echocardiographic Study

ObjectivesThe goal of this study was to define electrocardiographic (ECG) and echocardiographic characteristics of adolescent African athletes.BackgroundRecent observations in African athletes reported large prevalence of left ventricular (LV) hypertrophy and ECG abnormalities. No data, so far, exist for adolescent Africans, which comprise a growing proportion of competitive/professional athletes.MethodsThe study included 154 soccer players participating at the 8th African Under-17 Championship of 2009, representing Algeria, Burkina Faso, Cameroon, Gambia, Guinea, Malawi, Nigeria, and Zimbabwe. For comparison, 62 Italian players with similar ages, sport achievements, and training schedules were included.ResultsAfrican athletes showed higher R5/S1-wave voltages than Caucasian athletes (48.6 ± 12.1 mm vs. 34.1 ± 8.9 mm; p < 0.01), larger prevalence of ECG LV hypertrophy (89% vs. 42%; p < 0.001), ST-segment elevation (91% vs. 56%; p < 0.001), and deeply inverted, or diffusely flat/biphasic, T waves (14% vs. 3% [p < 0.05] and 25% vs. 8% [p < 0.008], respectively). LV wall thicknesses were increased in Africans by 5% compared with Caucasians, and exceeded normal limits (≥13 mm) in 4 Africans but in no Caucasians. No athlete showed evidence of cardiomyopathies (i.e., hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy). On individual analysis, Algerians showed lower R/S-wave voltages compared with other African athletes. Increased wall thickness (≥13 mm) was observed only in sub-Saharian athletes (from Burkina Faso, Cameroon, and Niger).ConclusionsAfrican athletes displayed large proportion of ECG abnormalities, including a striking increase in R/S-wave voltage, ST-segment elevation, and deeply inverted or diffusely flat T waves by adolescence. LV remodeling in African athletes was characterized by a disproportionate wall thickening than in Caucasians but similar cavity size. Finally, distinctive peculiarities existed in African athletes according to the country (and ethnic) origin

Injuries in male and female semi-professional football (soccer) players in Nigeria: prospective study of a National Tournament

BACKGROUND: Research on the epidemiology of football injuries in Africa is very sparse despite its importance for injury prevention planning in a continent with limited sports medicine resources. The vast majority of studies available in literature were conducted in Europe and only a very few studies have prospectively reported the pattern of football injury in Africa. The purpose of this study was to evaluate the incidence and pattern of injuries in a cohort of male and female semi-professional football players in Nigeria. METHODS: A prospective cohort design was conducted, in which a total of 756 players with an age range of 18–32 years (356 males and 300 females) from 22 different teams (12 male and 10 female teams), were prospectively followed in a National Football Tournament. Physiotherapists recorded team exposure and injuries. Injuries were documented using the consensus protocol for data collection in studies relating to football injury surveillance. RESULTS: An overall incidence of 113.4 injuries/1000 h (95% CI 93.7–136.0) equivalent to 3.7 injuries/match and time-loss incidence of 15.6 injuries/1000 h were recorded for male players and 65.9 injuries/1000 h (95% CI 48.9–86.8) equivalent to 2.2 injuries/match and time-loss incidence of 7.9 injuries/1000 h were recorded for female players. Male players had a significantly higher risk of injuries [IRR = 1.72 (95% CI 1.23–2.45)]. Injuries mostly affected the lower extremity for both genders (n = 81, 70% and n = 31, 62% for males and females respectively). Lower leg contusion (n = 22, 19%) and knee sprain (n = 9, 18%) were the most common specific injury types for male and female players respectively. Most of the injuries were as a result of contact with another player (n = 102, 88%—males; n = 48, 96%—females). Time-loss injuries were mostly estimated as minimal (n = 11, 69%) for male players and severe (n = 4, 66%) for female players. CONCLUSION: The overall incidence of injuries among Nigerian semi-professional football players is high but most of the injuries do not result in time-loss. Pattern of injuries is mostly consistent with previous studies. More prospective studies are needed to establish injury prevention initiatives among African players

Training during the COVID-19 lockdown : knowledge, beliefs, and practices of 12,526 athletes from 142 countries and six continents

OBJECTIVE Our objective was to explore the training-related knowledge, beliefs, and practices of athletes and the influence of lockdowns in response to the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS Athletes (n = 12,526, comprising 13% world class, 21% international, 36% national, 24% state, and 6% recreational) completed an online survey that was available from 17 May to 5 July 2020 and explored their training behaviors (training knowledge, beliefs/attitudes, and practices), including specific questions on their training intensity, frequency, and session duration before and during lockdown (March–June 2020). RESULTS Overall, 85% of athletes wanted to “maintain training,” and 79% disagreed with the statement that it is “okay to not train during lockdown,” with a greater prevalence for both in higher-level athletes. In total, 60% of athletes considered “coaching by correspondence (remote coaching)” to be sufficient (highest amongst world-class athletes). During lockdown, < 40% were able to maintain sport-specific training (e.g., long endurance [39%], interval training [35%], weightlifting [33%], most (83%) training for “general fitness and health maintenance” during lockdown. Athletes trained alone (80%) and focused on bodyweight (65%) and cardiovascular (59%) exercise/training during lockdown. Compared with before lockdown, most athletes reported reduced training frequency (from between five and seven sessions per week to four or fewer), shorter training sessions (from ≥ 60 to < 60 min), and lower sport-specific intensity (~ 38% reduction), irrespective of athlete classification. CONCLUSIONS COVID-19-related lockdowns saw marked reductions in athletic training specificity, intensity, frequency, and duration, with notable within-sample differences (by athlete classification). Higher classification athletes had the strongest desire to “maintain” training and the greatest opposition to “not training” during lockdowns. These higher classification athletes retained training specificity to a greater degree than others, probably because of preferential access to limited training resources. More higher classification athletes considered “coaching by correspondence” as sufficient than did lower classification athletes. These lockdown-mediated changes in training were not conducive to maintenance or progression of athletes’ physical capacities and were also likely detrimental to athletes’ mental health. These data can be used by policy makers, athletes, and their multidisciplinary teams to modulate their practice, with a degree of individualization, in the current and continued pandemic-related scenario. Furthermore, the data may drive training-related educational resources for athletes and their multidisciplinary teams. Such upskilling would provide athletes with evidence to inform their training modifications in response to germane situations (e.g., COVID related, injury, and illness).A specific funding was provided by the National Sports Institute of Malaysia for this study.The National Sports Institute of Malaysia.https://www.springer.com/journal/40279am2023Sports Medicin

COVID-19 lockdown : a global study investigating athletes’ sport classification and sex on training practices

PURPOSE : To investigate differences in athletes’ knowledge, beliefs, and training practices during COVID-19 lockdowns with reference to sport classification and sex. This work extends an initial descriptive evaluation focusing on athlete classification. METHODS : Athletes (12,526; 66% male; 142 countries) completed an online survey (May–July 2020) assessing knowledge, beliefs, and practices toward training. Sports were classified as team sports (45%), endurance (20%), power/technical (10%), combat (9%), aquatic (6%), recreational (4%), racquet (3%), precision (2%), parasports (1%), and others (1%). Further analysis by sex was performed. RESULTS : During lockdown, athletes practiced body-weight-based exercises routinely (67% females and 64% males), ranging from 50% (precision) to 78% (parasports). More sport-specific technical skills were performed in combat, parasports, and precision (∼50%) than other sports (∼35%). Most athletes (range: 50% [parasports] to 75% [endurance]) performed cardiorespiratory training (trivial sex differences). Compared to prelockdown, perceived training intensity was reduced by 29% to 41%, depending on sport (largest decline: ∼38% in team sports, unaffected by sex). Some athletes (range: 7%–49%) maintained their training intensity for strength, endurance, speed, plyometric, change-of-direction, and technical training. Athletes who previously trained ≥5 sessions per week reduced their volume (range: 18%–28%) during lockdown. The proportion of athletes (81%) training ≥60 min/session reduced by 31% to 43% during lockdown. Males and females had comparable moderate levels of training knowledge (56% vs 58%) and beliefs/attitudes (54% vs 56%). CONCLUSIONS : Changes in athletes’ training practices were sport-specific, with few or no sex differences. Team-based sports were generally more susceptible to changes than individual sports. Policy makers should provide athletes with specific training arrangements and educational resources to facilitate remote and/or home-based training during lockdown-type events.https://journals.humankinetics.com/view/journals/ijspp/ijspp-overview.xmlhj2023Sports Medicin

Cartographie de la controverse d’exploration et d’exploitation du gaz de schiste en Algérie

En Algérie, la nouvelle loi sur les hydrocarbures autorise l’exploitation des hydrocarbures non conventionnels, incluant le gaz de schiste, dont les réserves ont récemment été réévaluées à la hausse. Ces rebondissements ont suscité autant l’intérêt que l’inquiétude de l’opinion publique. Très sommairement, le débat est perçu comme opposant les « pour » l’exploitation qui mettent en avant des gains économiques aux « contre », écologistes s’opposant à la fracturation hydraulique. Cette dualité ne rend pas justice à la complexité de la controverse. Le but de ce travail est donc de percevoir clairement les enjeux liés à la controverse en mettant de l’avant la complexité et la variété des argumentaires présentés à travers une cartographie de la controverse. Nous souhaitons, par la même occasion, démontrer qu’une bonne compréhension des dynamiques et des processus de conflits exprimés par la controverse est nécessaire et décisive pour le processus d’acceptabilité sociale.In Algeria, the new hydrocarbon law authorizes the exploitation of unconventional oil and gas, including shale gas, in addition to that Algerian reserves have recently been revalued upward. These twists have attracted the interest and concerns of the public. Very roughly, the debate is seen as opposing those for a shale gas operation, who highlight the financial gains to those against any shale gas operation, environmentalists, arguing the dangers of hydraulic fracturing. This duality does not do represent truly the complexity of the controversy. The purpose of this work is to clearly perceive the issues related to the controversy by putting forward the variety of opposing arguments presented through an extensive mapping the controversy. In addition to that we aim to demonstrate that a good representation and thus understanding of conflict dynamics and processes expressed through the controversy is necessary and crucial for the social acceptability process

La variabilité des temps de déplacement des voyageurs : élaboration d'un modèle de valorisation et conséquences dans le calcul économique.

CD Rom éditionInternational audienceLes gains de temps sont calculés sous forme cumulée en se référant à une valeur monétaire moyenne et dépourvue de toute notion rendant compte de la qualité du temps gagné ou perdu notamment dans le transport par voiture particulière. Quoi qu'il en soit, l'évaluation de ces gains sous forme d'indicateur agrégé et unique est une approche réductrice, négligeant l'essentiel des aspects qui s'attachent aux notions de régularité et de confort dans lesquelles se réalisent les déplacements. Aussi pour mieux évaluer les effets des investissements et des actions d'exploitation, et pour des besoins correspondants de modélisation des flux de trafic routier et de la mobilité en général, faut-il se reposer la question de savoir comment intervient le temps dans la perception qu'ont les usagers du système de transport

La valeur de la fiabilité des durées d'acheminement dans le transport ferroviaire de fret

National audienceLe succès d'un service de transport de marchandises se mesure de plus en plus au respect des engagements conclus avec le client en termes de " qualité ". Cette qualité de service s'exprime comme le bon respect des heures convenues, entre le transporteur et le chargeur, d'arrivée de la marchandise au lieu de sa destination. Le but de ces travaux de recherche est de définir des indicateurs caractérisant la fiabilité des durées de trajet, de les quantifier à partir des données disponibles sur le réseau ferroviaire et de mettre au point une méthodologie permettant d'évaluer les gains engendrés par des actions, des stratégies ou des investissements œuvrant à l'amélioration de la fiabilité du transport ferroviaire. Par ailleurs, ce cadre méthodologique permettra au chargeur d'optimiser son stock en réduisant son incertitude sur la durée d'acheminement de sa marchandise à destination, au transporteur d'optimiser son service, au gestionnaire d'infrastructure d'optimiser le fonctionnement du système ferroviaire et à la collectivité (pouvoirs publics) d'optimiser ses investissements en matière de transport et d'inscrire cette activité, vitale et nécessaire à l'économie nationale, dans le développement durable