91 research outputs found
Ergodic properties of a model for turbulent dispersion of inertial particles
We study a simple stochastic differential equation that models the dispersion
of close heavy particles moving in a turbulent flow. In one and two dimensions,
the model is closely related to the one-dimensional stationary Schroedinger
equation in a random delta-correlated potential. The ergodic properties of the
dispersion process are investigated by proving that its generator is
hypoelliptic and using control theory
ICASENSE : une application de l'analyse en composantes indépendantes à l'IRM parallèle
Les récentes méthodes d'imagerie IRM parallèle (SENSE et SMASH) nécessitent une bonne connaissance de la sensibilité des antennes. Celle ci est généralement mesurée lors d'une phase de calibration, ou estimée par filtrage adaptatif spatio-temporel si l'on dispose d'une série d'acquisitions (TSENSE). Nous proposons une formulation du problème en termes de séparation aveugle de sources : une analyse en composantes indépendantes (ICA) permet alors d'extraire les informations de sensibilité des antennes à partir d'une seule acquisition. Des résultats de simulations sont présentés, démontrant l'intérêt de cette nouvelle méthode que nous nommerons ICASENSE
A lattice estimate of the g_{D^* D pi} coupling
We present the results of the first direct determination of the g_{D^* D pi}
coupling using lattice QCD. From our simulations in the quenched approximation,
we obtain g_{D^* D pi} = 18.8 +/- 2.3^{+1.1}_{-2.0} and hat(g) = 0.67 +/-
0.08^{+0.04}_{-0.06}. It is in agreement with a recent experimental result from
CLEO.Comment: Lattice2002(heavyquark), 3 pages, 3 figure
Systematic analyses of the MIR172 family members of Arabidopsis define their distinct roles in regulation of APETALA2 during floral transition
Particles and fields in fluid turbulence
The understanding of fluid turbulence has considerably progressed in recent
years. The application of the methods of statistical mechanics to the
description of the motion of fluid particles, i.e. to the Lagrangian dynamics,
has led to a new quantitative theory of intermittency in turbulent transport.
The first analytical description of anomalous scaling laws in turbulence has
been obtained. The underlying physical mechanism reveals the role of
statistical integrals of motion in non-equilibrium systems. For turbulent
transport, the statistical conservation laws are hidden in the evolution of
groups of fluid particles and arise from the competition between the expansion
of a group and the change of its geometry. By breaking the scale-invariance
symmetry, the statistically conserved quantities lead to the observed anomalous
scaling of transported fields. Lagrangian methods also shed new light on some
practical issues, such as mixing and turbulent magnetic dynamo.Comment: 165 pages, review article for Rev. Mod. Phy
Progress of the LUNEX5 Project
http://accelconf.web.cern.ch/AccelConf/FEL2013/papers/wepso05.pdfInternational audienceLUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region. A 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), will feed a single Free Electron Laser line with High order Harmonic in Gas and Echo Enable Harmonic Generation seeding. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies of a LWFA based on more realistic beam parameters (1 % energy spread, 1 ÎĽm beam size and 1 mrad divergence) than the ones assumed in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. It is noted in this context that among the French scientific community's interest in experiments at operating FELs is increasing
Lyapunov Exponents for Particles Advected in Compressible Random Velocity Fields at Small and Large Kubo Numbers
AAV-mediated in vivo knockdown of luciferase using combinatorial RNAi and U1i
RNA interference (RNAi) has been successfully employed for specific inhibition of gene expression; however, safety and delivery of RNAi remain critical issues. We investigated the combinatorial use of RNAi and U1 interference (U1i). U1i is a gene-silencing technique that acts on the pre-mRNA by preventing polyadenylation. RNAi and U1i have distinct mechanisms of action in different cellular compartments and their combined effect allows usage of minimal doses, thereby avoiding toxicity while retaining high target inhibition. As a proof of concept, we investigated knockdown of the firefly luciferase reporter gene by combinatorial use of RNAi and U1i, and evaluated their inhibitory potential both in vitro and in vivo. Co-transfection of RNAi and U1i constructs showed additive reduction of luciferase expression up to 95% in vitro. We attained similar knockdown when RNAi and U1i constructs were hydrodynamically transfected into murine liver, demonstrating for the first time successful in vivo application of U1i. Moreover, we demonstrated long-term gene silencing by AAV-mediated transduction of murine muscle with RNAi/U1i constructs targeting firefly luciferase. In conclusion, these results provide a proof of principle for the combinatorial use of RNAi and U1i to enhance target gene knockdown in vivo
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