A theoretical approach for analyzing the restabilization of wakes

Recently reported experimental results demonstrate that restabilization of the low-Reynolds-number flow past a circular cylinder can be achieved by the placement of a smaller cylinder in the wake of the first at particular locations. Traditional numerical procedures for modeling such phenomena are computationally expensive. An approach is presented here in which the properties of the adjoint solutions to the linearized equations of motion are exploited to map quickly the best positions for the small cylinder's placement. Comparisons with experiment and previous computations are favorable. The approach is shown to be applicable to general flows, illustrating how strongly control mechanisms that involve sources of momentum couple to unstable (or stable) modes of the system

Variational calculation of many-body wave functions and energies from density-functional theory

A generating coordinate is introduced into the exchange-correlation functional of density-functional theory (DFT). The many-body wave function is represented as a superposition of Kohn-Sham (KS) Slater determinants arising from different values of the generating coordinate. This superposition is used to variationally calculate many-body energies and wave functions from solutions of the KS equation of DFT. The method works for ground and excited states, and does not depend on identifying the KS orbitals and energies with physical ones. Numerical application to the Helium isoelectronic series illustrates the method's viability and potential.Comment: 4 pages, 2 tables, J. Chem. Phys., accepte

Design and development of a theory-informed peer-led falls prevention education programme to translate evidence into practice: A systematic approach

Peer-led education has been shown to be an effective approach for raising community-dwelling older adults’ beliefs, knowledge and intention to engage in falls prevention strategies in a recent intervention trial. This article outlines the design and development of the intervention, which was a peer-led falls prevention education programme designed to promote older adult’s motivation to change their behaviour in the area of falls prevention. The elements of the programme that contributed to its efficacy are also described. The programme was designed using a four-step approach and was based on the constructs of a theoretical framework (the COM-B model). Feedback from older adults was also incorporated into the programme development. Programme components developed were a workshop to train older adult peer educators to deliver falls prevention education, a one-hour peer-led falls prevention presentation, and supporting resources to aid programme delivery. A questionnaire measuring older adults’ responses to the presentation was concurrently developed and pilot-tested prior to implementation of the education programme. Finally, resources to monitor and evaluate fidelity at five points in the programme were developed. It was found that seeking older adult consumer involvement, and adopting a theoretical framework-driven approach contributes to effective design and delivery of falls prevention education programmes. This ensured that the programme was acceptable to older adults, feasible to deliver and allowed robust measurement of the effect of the education programme on important behavioural change components

Large-eddy simulation and multiscale modelling of a Richtmyer–Meshkov instability with reshock

Large-eddy simulations of the Richtmyer–Meshkov instability with reshock are pre- sented and the results are compared with experiments. Several configurations of shocks initially travelling from light (air) to heavy (sulfur hexafluoride, SF6) have been simulated to match previous experiments and good agreement is found in the growth rates of the turbulent mixing zone (TMZ). The stretched-vortex subgrid model used in this study allows for subgrid continuation modelling, where statistics of the unresolved scales of the flow are estimated. In particular, this multiscale modelling allows the anisotropy of the flow to be extended to the dissipation scale, eta, and estimates to be formed for the subgrid probability density function of the mixture fraction of air/SF6 based on the subgrid variance, including the effect of Schmidt number

Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes

Dispersive Alfven waves (DAWs) offer, an alternative to magnetic reconnection, opportunity to accelerate solar flare particles. We study the effect of DAW polarisation, L-, R-, circular and elliptical, in different regimes inertial and kinetic on the efficiency of particle acceleration. We use 2.5D PIC simulations to study how particles are accelerated when DAW, triggered by a solar flare, propagates in transversely inhomogeneous plasma that mimics solar coronal loop. (i) In inertial regime, fraction of accelerated electrons (along the magnetic field), in density gradient regions is ~20% by the time when DAW develops 3 wavelengths and is increasing to ~30% by the time DAW develops 13 wavelengths. In all considered cases ions are heated in transverse to the magnetic field direction and fraction of the heated particles is ~35%. (ii) The case of R-circular, L- and R- elliptical polarisation DAWs, with the electric field in the non-ignorable transverse direction exceeding several times that of in the ignorable direction, produce more pronounced parallel electron beams and transverse ion beams in the ignorable direction. In the inertial regime such polarisations yield the fraction of accelerated electrons ~20%. In the kinetic regime this increases to ~35%. (iii) The parallel electric field that is generated in the density inhomogeneity regions is independent of m_i/m_e and exceeds the Dreicer value by 8 orders of magnitude. (iv) Electron beam velocity has the phase velocity of the DAW. Thus electron acceleration is via Landau damping of DAWs. For the Alfven speeds of 0.3c the considered mechanism can accelerate electrons to energies circa 20 keV. (v) The increase of mass ratio from m_i/m_e=16 to 73.44 increases the fraction of accelerated electrons from 20% to 30-35% (depending on DAW polarisation). For the mass ratio m_i/m_e=1836 the fraction of accelerated electrons would be >35%.Comment: Final accepted version. To appear in Physics of Plasmas, volume 18, issue 9 (September 2011

Do peers increase older adults\u27 participation in strength training? Pilot randomized trial

Fewer than 20% of older adults participate in strength training (ST). Barriers to ST participation include not knowing where to go or not having someone to go with. To address these barriers, the authors provided older adults with a peer (older person already participating in ST) to support their engagement. The aim of this pilot randomized controlled trial was to determine whether older adults who were provided with a peer when participating in ST were more likely to be participating in ST 4 weeks postintervention, compared with those receiving ST alone. Fifty-one ST participants were recruited; 40 completed the intervention and postintervention data collection (78.4%). Providing peer support with ST did not significantly increase ST participation (p = .775). However, both groups made significant improvements over time in lower-limb strength and mobility. Participants in either group who continued the ST program (55%) had made additional significant improvements in lower-limb strength and mobility

Gates for the Kane Quantum Computer in the Presence of Dephasing

In this paper we investigate the effect of dephasing on proposed quantum gates for the solid-state Kane quantum computing architecture. Using a simple model of the decoherence, we find that the typical error in a CNOT gate is $8.3 \times 10^{-5}$. We also compute the fidelities of Z, X, Swap, and Controlled Z operations under a variety of dephasing rates. We show that these numerical results are comparable with the error threshold required for fault tolerant quantum computation.Comment: 9 pages, 9 figure