The elephant mode between two rotating disks

International audienceSpectral direct numerical simulations (DNS) are carried out for a source-sink flow in an annular cavity between two co-rotating disks. When the Reynolds number based on the forced inflow is increased, a self-sustained crossflow instability of finite amplitude is observed. We show that this nonlinear global mode is made up of a front located at the upstream boundary of the absolutely unstable domain, followed by a saturated spiral mode, and that its properties are in good agreement with results of the local stability theory. This structure is characteristic of the so-called elephant mode of Pier & Huerre (J. Fluid Mech. vol. 435, 2001, p. 145). The global bifurcation is subcritical since only large-amplitude initial perturbations are found to trigger the elephant mode. Small-amplitude perturbations induce a long-lasting transient growth but lead eventually to a damped linear global mode, showing that non-parallel effects counteract the absolute instability and restabilize the flow. A similar linear global stabilization due to non-parallel effects has been found in the case of the flow above a single rotating disk. For the single-disk geometry, the existence of an elephant mode would imply, together with results of Davies & Carpenter (2003) a subcritical global instability, which has not yet been demonstrated. Although the present geometry differs from the single-disk case, the existence of a subcritical global bifurcation is now established, allowing a precise analysis of the transition scenarios. © 2008 Cambridge University Press

Transition to turbulence through steep global-modes cascade in an open rotating cavity

International audienceThe transition to turbulence in a rotating boundary layer is analysed via direct numerical simulation (DNS) in an annular cavity made of two parallel corotating discs of finite radial extent, with a forced inflow at the hub and free outflow at the rim. In a former numerical investigation (Viaud, Serre & Chomaz J. Fluid Mech., vol. 598, 2008, pp. 451-464) realized in a sectorial cavity of azimuthal extent 2p68, we have established the existence of a primary bifurcation to nonlinear global mode with angular phase velocity and radial envelope coherent with the so-called elephant mode theory. The former study has demonstrated the subcritical nature of this primary bifurcation with a base flow that keeps being linearly stable for all Reynolds numbers studied. The present work investigates the stability of this elephant mode by extending the cavity both in the radial and azimuthal direction. When the Reynolds number based on the forced throughflow is increased above a threshold value for the existence of the nonlinear global mode, a large-amplitude impulsive perturbation gives rise to a self-sustained saturated wave with characteristics identical to the 68-fold global elephant mode obtained in the smaller cavity. This saturated wave is itself globally unstable and a second front appears in the lee of the primary where small-scale instability develops. These secondary instabilities are identical for the 2p/68 and the 2p/4 long sectorial cavities, indicating that transition involves a Floquet mode of zero azimuthal wavenumber. This secondary instability leads to a very disorganized state, defining the transition to turbulence. The observed transition to turbulence linked to the secondary instability of a global mode confirms, for the first time on a real flow, the possibility of a direct transition to turbulence through an elephant mode cascade, a scenario that was up to now only observed on the Ginzburg-Landau model. © 2011 Cambridge University Press

Reweighting of the form factors in exclusive B --> X ell nu decays

A form factor reweighting technique has been elaborated to permit relatively easy comparisons between different form factor models applied to exclusive B --> X l nu decays. The software tool developped for this purpose is described. It can be used with any event generator, three of which were used in this work: ISGW2, PHSP and FLATQ2, a new powerful generator. The software tool allows an easy and reliable implementation of any form factor model. The tool has been fully validated with the ISGW2 form factor hypothesis. The results of our present studies indicate that the combined use of the FLATQ2 generator and the form factor reweighting tool should play a very important role in future exclusive |Vub| measurements, with largely reduced errors.Comment: accepted for publication by EPJ

Automatic CX Tool for Electrical Building

Commissioning (Cx) consists in specifying building system performance requirements set by the owner, auditing different judgments and actions performed by the Cx related parties in order to achieve the performance, writing necessary and sufficient documentation, and verifying that the system enables proper operation and maintenance through functional performance testing. The process of Cx is the whole set of tasks ensuring that the performance of buildings meet the awaited performance. This process comes within the scope of Kyoto's protocol by reducing energy consumption and also emission of green house gases (GHG). This study is carried out for an exemplary electrical building of educational facilities. The objectives of the project are to develop and test a Cx tool in order to increase the energy efficiency of the building while ensuring indoor comfort. This study shows that an appropriate design of a building is not sufficient to ensure an effective management of energy. The Cx of installations is an essential step to meet the required energy performances

The IEA/ECBCS/Annex 40 Glossary on Commissioning

International Energy Agency's (IEA) Energy Conservation in Building and Community Systems' (ECBCS) Annex 40 has developed a glossary of commissioning terms as one of the first commissioning tools produced within the annex. The glossary consists of four major sections: 1) definition of basic terms, 2) explanation of basic terms, 3) commissioning types, and 4) commissioning process. These sections, which were originally developed to facilitate Annex 40 discussions, are now incorporated into an on-line database system. This on-line tool is publicly available on the Annex 40 website and enables users to search for specific definitions and provides links for more detailed explanations, related terms, and existing reference definitions. Using this database system many documents developed in Annex 40 have been actively linked to the glossary for direct access to the definitions. In addition, during the development and review process for the glossary, users are able to submit suggestions for new terms, translations, and other modifications. The purpose of this paper is to introduce the glossary and database system developed in Annex 40 and to invite users to participate in the public review of the glossary before publication of the final report

Crab Waist Scheme Luminosity and Background Diagnostic at DAFNE

TUPTPF029International audienceTest of the crab waist scheme, undergoing at the Frascati DAFNE accelerator complex, needs a fast and accurate measurement of the luminosity, as well as a full characterization of the background conditions. Three different monitors, a Bhabha calorimeter, a Bhabha GEM tracker and a gamma bremsstrahlung proportional counter have been designed, tested and installed on the accelerator at the end of January 2008. Results from beam-test measurements, comparison with the Monte Carlo simulation and preliminary data collected during the SIDDHARTA run are presented

Aganirsen Antisense Oligonucleotide Eye Drops Inhibit Keratitis-Induced Corneal Neovascularization and Reduce Need for Transplantation: The I-CAN Study.

OBJECTIVE: Eye drops of aganirsen, an antisense oligonucleotide preventing insulin receptor substrate-1 expression, inhibited corneal neovascularization in a previous dose-finding phase II study. We aimed to confirm these results in a phase III study and investigated a potential clinical benefit on visual acuity (VA), quality of life (QoL), and need for transplantation. DESIGN: Multicenter, double-masked, randomized, placebo-controlled phase III study. PARTICIPANTS: Analysis of 69 patients with keratitis-related progressive corneal neovascularization randomized to aganirsen (34 patients) or placebo (35 patients). Patients applied aganirsen eye drops (86 μg/day/eye) or placebo twice daily for 90 days and were followed up to day 180. MAIN OUTCOME MEASURES: The primary end point was VA. Secondary end points included area of pathologic corneal neovascularization, need for transplantation, risk of graft rejection, and QoL. RESULTS: Although no significant differences in VA scores between groups were observed, aganirsen significantly reduced the relative corneal neovascularization area after 90 days by 26.20% (P = 0.014). This improvement persisted after 180 days (26.67%, P = 0.012). Aganirsen tended to lower the transplantation need in the intent-to-treat (ITT) population at day 180 (P = 0.087). In patients with viral keratitis and central neovascularization, a significant reduction in transplantation need was achieved (P = 0.048). No significant differences between groups were observed in the risk of graft rejection. However, aganirsen tended to decrease this risk in patients with traumatic/viral keratitis (P = 0.162) at day 90. The QoL analyses revealed a significant improvement with aganirsen in composite and near activity subscores (P = 0.039 and 0.026, respectively) at day 90 in the per protocol population. Ocular and treatment-related treatment-emergent adverse events (TEAEs) were reported in a lower percentage with aganirsen compared with placebo. Only 3 serious TEAEs (2 with aganirsen and 1 with placebo) were considered treatment-related. CONCLUSIONS: This first phase III study on a topical inhibitor of corneal angiogenesis showed that aganirsen eye drops significantly inhibited corneal neovascularization in patients with keratitis. The need for transplantation was significantly reduced in patients with viral keratitis and central neovascularization. Topical application of aganirsen was safe and well tolerated

Quantum numbers of the X(3872)X(3872) state and orbital angular momentum in its ρ0Jψ\rho^0 J\psi decay

Angular correlations in $B^+\to X(3872) K^+$ decays, with $X(3872)\to \rho^0 J/\psi$, $\rho^0\to\pi^+\pi^-$ and $J/\psi \to\mu^+\mu^-$, are used to measure orbital angular momentum contributions and to determine the $J^{PC}$ value of the $X(3872)$ meson. The data correspond to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be $J^{PC}=1^{++}$. The $X(3872)$ is found to decay predominantly through S wave and an upper limit of $4\%$ at $95\%$ C.L. is set on the fraction of D wave.Comment: 16 pages, 4 figure