A phase transition in a system driven by coloured noise

For a system driven by coloured noise, we investigate the activation energy of escape, and the dynamics during the escape. We have performed analogue experiments to measure the change in activation energy as the power spectrum of the noise varies. An adiabatic approach based on path integral theory allows us to calculate analytically the critical value at which a phase transition in the activation energy occurs

Orbital damping of the oscillating superfluid He A-B interface at low temperatures

We present a model for the friction and effective mass of an oscillating superfluid He A-B interface due to orbital viscosity in the B-phase texture close to the interface. The model is applied to an experiment in which the A-B interface was stabilised in a magnetic field gradient at the transition field mT at 0 bar pressure and at a very low temperature mK. The interface was then oscillated by applying a small additional field at frequencies in the range 0.1-100 Hz. The response of the interface is governed by friction and by its effective mass. The measured dissipation does not fit theoretical predictions based either on the Andreev scattering of thermal quasiparticles or by pair-breaking from the moving interface. We describe a new mechanism based on the redistribution of thermal quasiparticle excitations in the B-phase texture engendered by the moving interface. This gives rise to friction via orbital viscosity and generates a significant effective mass of the interface. We have incorporated this mechanism into a simple preliminary model which provides reasonable agreement with the measured behaviour

Symmetry breaking of fluctuation dynamics by noise color.

Activated escape is investigated for systems that are driven by noise whose power spectrum peaks at a finite frequency. Analytic theory and analog and digital experiments show that the system dynamics during escape exhibit a symmetry-breaking transition as the width of the fluctuational spectral peak is varied. For double-well potentials, even a small asymmetry may result in a parametrically large difference of the activation energies for escape from different wells

Experimental studies of the non-adiabatic escape problem

Noise-induced transitions between coexisting stable states of a periodically driven nonlinear oscillator have been investigated by means of analog experiments and numerical simulations in the nonadiabatic limit for a wide range of oscillator parameters. It is shown that, for over-damped motion, the field-induced corrections to the activation energy can be described quantitatively in terms of the logarithmic susceptibility (LS) and that the measured frequency dispersion of the corresponding corrections for a weakly damped nonlinear oscillator is in qualitative agreement with the theoretical prediction. Resonantly directed diffusion is observed in numerical simulations of a weakly damped oscillator. The possibility of extending the LS approach to encompass escape from the basin of attraction of a quasi-attractor is discussed

The Kramers problem:beyond quasi-stationarity

Noise-induced escape from a metastable potential is considered on time-scales preceding the formation of quasi-equilibrium within the metastable part of the potential. It is shown that the escape flux may then depend exponentially strongly, and in a complicated manner, on time and friction

Budget impact analysis of medicines : updated systematic review and implications

This evaluation determines whether published studies to date meet the key characteristics identified for budget impact analyses (BIA) for medicines, accomplished through a systematic review and assessment against identified key characteristics. Studies from 2001 to 2015 on "budget impact analysis" with "drug" interventions were assessed, selected based on their titles/abstracts and full texts, with their characteristics checked according to key criteria. Out of 1984 studies, 92 were identified. Of these, 95% were published in Europe and the USA. 2012 saw the largest number of publications (16%) with a decline thereafter. 48% met up to 6 or 7 out of the 9 key characteristics. Only 22% stated no conflict of interest. The results indicate low adherence to the key characteristics that should be considered for BIAs and strong conflict of interest. This is an issue since BIAs can be of fundamental importance in managing the entry of new medicines including reimbursement decisions

Optimal paths and large fluctuations

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN026655 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Dispersion of the prehistory distribution : analog experiments and numerical results.

The dispersion parameter of the prehistory distribution for a potential system driven by white noise is analyzed theoretically and by means of analog and digital experiments. Nonmonotonic evolution of the dispersion with time is shown to arise provided that the potential fulfills a certain condition. It does not necessitate the existence of an unstable point, but can occur in single-minimum potentials, both symmetric and asymmetric