Coping and Resilience Among Endurance Athletes During the COVID-19 Pandemic

COVID-19 lockdowns constrained the training opportunities of athletes resulting in physical and mental hardship. In this study, athletes involved in the outdoor endurance sports of running, cycling or swimming were recruited through Facebook groups and using online mailing lists. The final sample (n = 3,551) consisted of 576 female respondents (16.2%), and 2,975 male respondents (83.8%). The mean age of participants was 44.13  years (min = 16, max = 83, and SD = 9.84). An online survey was designed to measure variables relevant to athletes’ mental health; resilience and emotion regulation strategies; mobility restrictions; training routines; personal involvement in endurance sports; age; gender; and country of residence. Overall, the results of our study indicate that during lockdown, decreases in training volume, lower lockdown-specific resilience, and holding more negative perceptions about lockdown mobility restrictions (perceived strictness) all contributed to perceived barriers to training. In the analysis, athletes’ relative observance of mobility restrictions was controlled for. Athletes exhibiting high personal commitment to their sports displayed: greater lockdown resilience, a greater use of adaptive coping strategies, and lower levels of perceived barriers to training

Nitrogen and water management can limit premature ripening of sunflower induced by Phoma macdonaldii

Premature ripening (PR) is one of the most important diseases of sunflower in France since the 90s. Previous results indicated that girdling canker of the stem base, caused by Phoma macdonaldii was its primary cause but elucidation of critical environmental factors involved is crucial for better control of the disease. A field study was conducted in three contrasting cropping seasons (2006–2008) and investigated the effect of N fertilization (0, 75 and 150 kg N ha−1) and water regime (rainfed, irrigated) on two cultivars with artificial inoculation (AI) and natural infection (NI). Disease assessment was recorded weekly to calculate the area under disease progress curve (AUDPC) and the final percentage of PR plants. Data showed that high levels of N fertilization led to significantly (P < 0.05) more PR than non-fertilization. Water deficit conditions were significantly (P < 0.05) involved in disease severity, and AUDPC and PR were increased when dry conditions were associated with high N supply. This was true for two cultivars which differed in their susceptibility to the disease but cv. Heliasol RM was significantly (P < 0.05) more affected than cv. Melody, partially resistant to PR. Despite contrasting weather patterns, these results demonstrated a clear role of crop management and environmental conditions on the incidence and severity of stem base attacks responsible for the PR syndrome. These findings suggest that sunflower crop husbandry should be adapted to minimize premature ripening induced by P. macdonaldii

Low plant density can reduce sunflower premature ripening caused by Phoma macdonaldii

In France, premature ripening (PR) is a widespread damage of a fungal disease of sunflower caused by Phoma macdonaldii. Previous results indicated that girdling canker at the stem base, caused by P. macdonaldii, was its primary cause. Previous studies have reported the influence of nitrogen and water supply on the incidence and severity of PR but an additional study was required to analyze the effect of plant density on the level of attack for a more comprehensive cultural control of PR. In a 2-year field study (2008 and 2009) in Toulouse (France), a susceptible cultivar (cv. Heliasol) artificially inoculated at star bud stage with P. macdonaldii was grown at three plant densities (4, 6.5 and 9 plants m−2) factorially combined with three N fertilization rates (0, 50/75 and 150 kg N ha−1) and two water regimes (irrigated and rainfed). P. macdonaldii symptoms were scored weekly to calculate the area under disease progress curve (AUDPC) and percentage of PR plants. Microclimatic conditions were monitored using thermo-hygrometers within the crop. The fraction of photosynthetically active radiation intercepted by the canopy (fPARi) and leaf area index (LAI) were measured at anthesis. Plant water status during the disease progression was characterized by crop simulation (SUNFLO) and N status at anthesis was assessed from shoot N content (Nm) analysis and N Nutrition Index (NNI) calculation. Increasing plant density resulted in a greater proportion of PR plants, and this proportion increased further when N was applied at 150 kg ha−1, the highest rate, and the crop was not irrigated. Despite differing canopy development, differences in microclimatic conditions between density levels were too small to explain the PR differences. However plant N concentration and diameter at stem base were closely related to PR incidence. Thin plants (grown at high density) with non-limiting N supply were the most susceptible to premature ripening. This study opens new avenues for the control of PR through crop management and emphasizes the key role of plant morphology in the development of the disease. Stem base diameter is a morphological trait that could be manipulated through crop management (plant density, N fertilization) and probably breeding in the future when developing integrated disease management systems in sunflower

Filtrage Stochastique et amélioration des performances des systèmes de positionnement d'engins sous-marins en milieu bruyant

Le positionnement d'un engin sous-marin s'appuie sur des systèmes dits "acoustiques". Ces derniers renseignent la position relative de l'engin immergé par rapport au navire support. Les performances de ces systèmes sont définies en termes de limite de portée et de précision. Le principe de ces systèmes repose sur les notions de distance-métrie et de goniométrie, qui s'appuient toutes deux sur l'estimation du temps de propagation et donc de la date d'arrivée du signal utile. Cela est classiquement réalisé par une opération de Compression d'Impulsion. Cette technique qui est largement utilisée dans les domaines du SONAR, RADAR et imagerie bio-médicale, repose sur une application sous-optimale du Filtrage Adapté. En effet, le Filtrage Adapté est une technique d estimation ou de détection optimale lorsque le bruit et blanc et gaussien et lorsque le signal utile est déterministe, c est-à-dire que le signal reçu est bien connu. Cependant, il est bien connu que dans le monde sous-marin, le bruit n est pas blanc, et pas toujours gaussien. Aussi, le signal utile étant déformé soit par le milieu de propagation soit par des phénomènes physiques tels que l effet Doppler, celui-ci n est pas déterministe. On peut alors considérer que le bruit est coloré et que le signal utile est une réalisation d un processus aléatoire. Ainsi, en vue d étendre les hypothèse d application de la Compression d Impulsion classique, nous proposons de construire une nouvelle forme de Compression d Impulsion basée sur l utilisation du Filtrage Adapté Stochastique. En effet, ce dernier est une extension naturelle du Filtrage Adapté pour des bruits colorés et des signaux déterministes. Toutefois, le Filtrage Adapté Stochastique suppose que les signaux sont stationnaires au second ordre. Or, cela n est pas toujours le cas pour le bruit en milieu marin, et cela n est jamais le cas pour un signal modulé en fréquence tel que ceux utilisés par les systèmes de positionnement acoustiques. Ainsi, nous proposons une nouvelle technique de Compression d Impulsion alliant les qualités du Filtrage Adapté Stochastique et celle des techniques Temps-Fréquence. Ces dernières, et en particulier la transformée de Wigner-Ville, permettent de contourner l hypothèse de stationnarité imposée par le Filtrage Adapté Stochastique. D autre part, en vue de contrer l apparition d interférences générées par ces techniques, nous développons ici une approche par décomposition atomique sur une base de DCT. Ainsi donc, ces trois années de thèse, ont donné naissance à de nouvelles méthodes de Compression d'Impulsion qui permettent d'améliorer les performances des systèmes de positionnement sous-marin.The underwater vehicules positioning is based on acoustic systems. These systems provide us the relative position of the immersed submarine to the carrier ship. The systems performances are defined in terms of precision and slant range. The positioning systems use concepts like distance measurement and goniometry, both based on the Time Of Arrival estimation of the useful signal, which is classically performed by a Pulse Compression. This technique, widely applied on SONAR, RADAR and bio-medical imaging, is a sub-optimal application of the Matched Filtering. After these three years of work, we had obtained new methods of Pulse Compression that allow to improve the performances of the acoustic positioning systems. These new techniques are based on an expension of the application assumptions of the Pulse Compression to reach, as well as possible, the optimality.TOULON-Bibliotheque electronique (830629901) / SudocSudocFranceF