Search results for "BES"
showing 10 items of 3692 documents
Étude des propriétés optiques et spectroscopiques de nanorods dopés au lanthanide pour des applications de nanosondes en champ proche
2022
Lanthanide-doped nanoparticles constitute a versatile family of photoluminescent local nanoprobes. In this work, we study the photoluminescence of Eu3+-doped NaYF4 nanorods characterized by highly polarized spectra. We develop a full theoretical model and paraxial approximation for nanorod dipole emission. We measure the photoluminescence of individual nanorods by fluorescence confocal microscopy and determine some of their intrinsic optical properties. We also determine the nature (electric or magnetic) and orientations of dipoles moments of the optical transitions used for nanoprobing in the visible range.In addition to the full theoretical model and the paraxial approximation, Fourier mi…
High speed cleaving of crystals with ultrafast Bessel beams
2017
International audience; We develop a novel concept for ultra-high speed cleaving of crystalline materials with femtosecond lasers. Using Bessel beams in single shot, fracture planes can be induced nearly all along the Bessel zone in sapphire. For the first time, we show that only for a pulse duration below 650 fs, a single fracture can be induced in sapphire, while above this duration, cracks appear in all crystallographic orientations. We determine the influential parameters which are polarization direction, crystallographic axes and scanning direction. This is applied to cleave sapphire with a spacing as high as 25 μm between laser impacts.
Micron-precision in cleaving glass using ultrafast bessel beams with engineered transverse beam shapes
2017
International audience; Ultrafast lasers in association to beam shaping have shown to be excellent candidates for transparent material processing. Non-diffractive solutions such as Bessel beams allows for precise energy deposition since they are robust to undesired non-linear effects and as they do not distort along the propagation. This offers important opportunities in laser-assisted cleaving, i.e. mechanical medium separation after single-pass laser illumination. Here we break the Bessel beam cylindrical symmetry using a novel anisotropic and non-diffractive solutions to investigate both lateral intensity contributions on material response and induced processing effect for non-cylindrica…
Evaluation of the areal material distribution of paper from its optical transmission image
2011
International audience; The goal of this study was to evaluate the areal mass distribution (defined as the X-ray transmission image) of paper from its optical transmission image. A Bayesian inversion framework was used in the related deconvolution process so as to combine indirect optical information with a priori knowledge about the type of paper imaged. The a priori knowledge was expressed in the form of an empirical Besov space prior distribution constructed in a computationally effective way using the wavelet transform. The estimation process took the form of a large-scale optimization problem, which was in turn solved using the gradient descent method of Barzilai and Borwein. It was de…
Obesity and Interpersonal Problems: An Analysis with the Interpersonal Circumplex
2012
This study examines the interpersonal problems profiles of obese individuals by cluster analysing the interpersonal problems circumplex scores of participants. The Inventory of Interpersonal Problems— Short Circumplex (IIP‐32) was completed by 368 treatment‐seeking obese individuals. These data were cluster analysed, and groups of obese subjects defined by varying interpersonal problems were compared with regard to psychological distress, self‐esteem, body dissatisfaction, quality of life and binge behaviours. Cluster analyses of the IIP‐32 resulted in four clusters, which occupied two quadrants of the interpersonal circumplex. Several differences in body mass index, psychological distress,…
CeLL, an agent based model for exploring the spatial influence influence of climate change on Lobesia botrana population dynamics
2016
International audience; The European Grapevine moth (Lobesia botrana) is one of the most noxious vineyard-pests in the European and Mediterranean area. Its larvae feed on grapevine flowers and berries, and usually cause considerable damage, also by facilitating saphrophytic infections to berries.The biology of L. botrana has been investigated since the 80s. A number of studies has tested its physiology and behaviour in experimental conditions (Hurtrel et Thiéry 1999), in field conditions (Stockel et al. 1994), and using mathematical modelling techniques. Whereas the modelling approaches that have been proposed in the literature are hetereogeneus they generally focus on the phenology and pop…
La lutte biologique contre l'ambroisie à feuilles d'armoise illustrée par l'exemple d'Ophraella communa: quels intérêts et quelles limites ?
2016
National audience; Common ragweed (Ambrosia artemisiifolia) was introduced in France over 150 years ago and its spreading across France now seems inexorable. The specific biology of this summer annual creates new problems for the managers of the various habitats where the plant can be found. The reduced possibility, or even the impossibility, to use traditional control means in certain environment conditions brings managers to consider biological control as one of the few possible means for slowing down the spread, or even pushing back the distribution area, of this invasive and allergenic plant. With Ophraella communa as an example, a reflection is presented on the benefit-risk balance of …
[CA-SYS] Avec les agriculteurs, mettre de l’ambition et du réalisme dans les questions de recherche en agroécologie
2019
National audience
La gestion des betteraves adventices résistantes à un herbicide: une approche par simulation
2007
National audience; Les variétés de betteraves sucrières génétiquement modifiées (GM) résistantes à un herbicide sont, a priori, intéressantes dans des champs fortement infestés par la betterave adventice. Cependant, la montée à fleurs de ces betteraves GM peut entraîner l’apparition d’individus résistants, via la dispersion de pollen. Nous avons développé et utilisé le modèle GENESYS-Betterave pour simuler, à l’échelle d’une petite région agricole, l’impact des pratiques culturales sur la dispersion du transgène. Il permet d'identifier des stratégies pour contrôler les adventices et limiter l'apparition de populations résistantes en zone de production de betterave sucrière. L’utilisation de…
Lipopolysaccharides and glucagon-like peptide 1 : from molecular mechanisms to pathophysiology
2016
Obesity and type 2 diabetes are metabolic diseases which have reached epidemic proportions worldwide. These metabolic disorders are related to a low grade inflammation whose molecular origin is still unknown. Previous studies have highlighted the involvement of the gut microbiota and especially components of the cell wall of Gram(-) bacteria: lipopolysaccharides (LPS). We have recently shown that LPS enhance glucagon-like peptide 1 (GLP-1) plasma levels, a hormone which is known to stimulate insulin secretion. Moreover there would be a link between the nutritional qualities of food and LPS plasma levels. Thus diet, LPS and GLP-1 may be closely related. The present work focuses on i) the mol…