Le GDR-Verres et l’USTV : des réseaux pour la réflexion scientifique sur des problématiques verrières académiques et industrielles

International audienceLa communauté scientifique et industrielle du verre est extraordinairement riche en France. Des équipes scientifiques avec une renommée internationale et une R&D verrière industrielle française, très dynamique, ayant besoin d’échanges sur des domaines d’expertise. Le réseau animé par le GDR-Verres et l’USTV crée un lien entre les équipes de recherche fondamentale, celles plus appliquée ou technologiques, et le monde industriel

Seismic entangled patterns analyzed via multiresolution decomposition

This article explores a method for distinguishing entangled coherent structures embedded in geophysical images. The original image is decomposed in a series of j-scale-images using multiresolution decomposition. To improve the image processing analysis each j-image is divided in l-spacial regions generating set of (j, l)-regions. At each (j, l)-region we apply a continuous wavelet transform to evaluate <i>E</i><sub>ν</sub>, the spectrum of energy. <i>E</i><sub>ν</sub> has two maxima in the original data. Otherwise, at each scale <i>E</i><sub>ν</sub> hast typically one peak. The localization of the peaks changes according to the (j, l)-region. The intensity of the peaks is linked with the presence of coherent structures, or patterns, at the respective (j, l)-region. The method is successfully applied to distinguish, in scale and region, the ground roll noise from the relevant geologic information in the signal

Dynamics of Elastic Excitable Media

The Burridge-Knopoff model of earthquake faults with viscous friction is equivalent to a van der Pol-FitzHugh-Nagumo model for excitable media with elastic coupling. The lubricated creep-slip friction law we use in the Burridge-Knopoff model describes the frictional sliding dynamics of a range of real materials. Low-dimensional structures including synchronized oscillations and propagating fronts are dominant, in agreement with the results of laboratory friction experiments. Here we explore the dynamics of fronts in elastic excitable media.Comment: Int. J. Bifurcation and Chaos, to appear (1999

Spatiotemporal Chaos, Localized Structures and Synchronization in the Vector Complex Ginzburg-Landau Equation

We study the spatiotemporal dynamics, in one and two spatial dimensions, of two complex fields which are the two components of a vector field satisfying a vector form of the complex Ginzburg-Landau equation. We find synchronization and generalized synchronization of the spatiotemporally chaotic dynamics. The two kinds of synchronization can coexist simultaneously in different regions of the space, and they are mediated by localized structures. A quantitative characterization of the degree of synchronization is given in terms of mutual information measures.Comment: 6 pages, using bifchaos.sty (included). 7 figures. Related material, including higher quality figures, could be found at http://www.imedea.uib.es/PhysDept/publicationsDB/date.html . To appear in International Journal of Bifurcation and Chaos (1999

Improvement of radiology requisition

AbstractPurposeInadequate or incomplete information on radiology requisitions may have a substantial impact on the radiological process. This study aimed to evaluate the impact of standardization and computerization of radiology requisitions on the quality of provided data, satisfaction of hospital staff and access time.MethodsThe impact of requisition support was assessed at each step of the improvement process for inpatients: before (Step 1), after standardization (Step 2) and after computerization of radiology requisition (Step 3). The quality of information provided was assessed by proportion of missing data on MRI and CT requisitions. Satisfaction was assessed by an anonymous auto-questionnaire filled by ordering physicians, radiologists and radiology technicians. Access time was prospectively assessed.ResultsStandardization of radiology requisition resulted in a significant drop in proportion of missing data. Computerization of radiology requisition, based on the single standardized radiology requisition, further improved the quality of information reported on radiology requisitions. The median access time was significantly improved (from 5 to 3days) for the largest provider of CT requisitions.ConclusionsStandardization and computerization have a synergistic effect on the overall quality improvement. Moreover, the computerized provider order entry enables traceability of information, makes communication between radiologists and ordering physicians easier and improves examination planning

Defect Chaos of Oscillating Hexagons in Rotating Convection

Using coupled Ginzburg-Landau equations, the dynamics of hexagonal patterns with broken chiral symmetry are investigated, as they appear in rotating non-Boussinesq or surface-tension-driven convection. We find that close to the secondary Hopf bifurcation to oscillating hexagons the dynamics are well described by a single complex Ginzburg-Landau equation (CGLE) coupled to the phases of the hexagonal pattern. At the bandcenter these equations reduce to the usual CGLE and the system exhibits defect chaos. Away from the bandcenter a transition to a frozen vortex state is found.Comment: 4 pages, 6 figures. Fig. 3a with lower resolution no

The Complex Ginzburg-Landau Equation in the Presence of Walls and Corners

We investigate the influence of walls and corners (with Dirichlet and Neumann boundary conditions) in the evolution of twodimensional autooscillating fields described by the complex Ginzburg-Landau equation. Analytical solutions are found, and arguments provided, to show that Dirichlet walls introduce strong selection mechanisms for the wave pattern. Corners between walls provide additional synchronization mechanisms and associated selection criteria. The numerical results fit well with the theoretical predictions in the parameter range studied.Comment: 10 pages, 9 figures; for related work visit http://www.nbi.dk/~martine

Wound-up phase turbulence in the Complex Ginzburg-Landau equation

We consider phase turbulent regimes with nonzero winding number in the one-dimensional Complex Ginzburg-Landau equation. We find that phase turbulent states with winding number larger than a critical one are only transients and decay to states within a range of allowed winding numbers. The analogy with the Eckhaus instability for non-turbulent waves is stressed. The transition from phase to defect turbulence is interpreted as an ergodicity breaking transition which occurs when the range of allowed winding numbers vanishes. We explain the states reached at long times in terms of three basic states, namely quasiperiodic states, frozen turbulence states, and riding turbulence states. Justification and some insight into them is obtained from an analysis of a phase equation for nonzero winding number: rigidly moving solutions of this equation, which correspond to quasiperiodic and frozen turbulence states, are understood in terms of periodic and chaotic solutions of an associated system of ordinary differential equations. A short report of some of our results has been published in [Montagne et al., Phys. Rev. Lett. 77, 267 (1996)].Comment: 22 pages, 15 figures included. Uses subfigure.sty (included) and epsf.tex (not included). Related research in http://www.imedea.uib.es/Nonlinea

Male Accessory Gland Protein Reduces Egg Laying in a Simultaneous Hermaphrodite

Seminal fluid is an important part of the ejaculate of internally fertilizing animals. This fluid contains substances that nourish and activate sperm for successful fertilization. Additionally, it contains components that influence female physiology to further enhance fertilization success of the sperm donor, possibly beyond the recipient's optimum. Although evidence for such substances abounds, few studies have unraveled their identities, and focus has been exclusively on separate-sex species. We present the first detailed study into the seminal fluid composition of a hermaphrodite (Lymnaea stagnalis). Eight novel peptides and proteins were identified from the seminal-fluid-producing prostate gland and tested for effects on oviposition, hatching and consumption. The gene for the protein found to suppress egg mass production, Ovipostatin, was sequenced, thereby providing the first fully-characterized seminal fluid substance in a simultaneous hermaphrodite. Thus, seminal fluid peptides and proteins have evolved and can play a crucial role in sexual selection even when the sexes are combined