Research shapes policy: but the dynamics are subtle

Major policy initiatives such as the Quality and Outcomes Framework (QOF) in the national contract for UK general practitioners might variably be informed by evidence at their inception, implementation and subsequent evolution. But what evidence gets admitted into these policy debates—and what is left out? Using QOF as an example, this article demonstrates what an analysis of the relationship between policy and the associated research can tell us about the underlying policy assumptions and about the role of evidence in policy debates

Radiation pressure-driven plasma surface dynamics in ultra-intense laser pulse interactions with ultra-thin foils

The dynamics of the plasma critical density surface in an ultra-thin foil target irradiated by an ultra-intense ( ∼ 6 × 1020 Wcm−2 ) laser pulse is investigated experimentally and via 2D particle-in- cell simulations. Changes to the surface motion are diagnosed as a function of foil thickness. The experimental and numerical results are compared with hole-boring and light-sail models of radi- ation pressure acceleration, to identify the foil thickness range for which each model accounts for the measured surface motion. Both the experimental and numerical results show that the onset of relativistic self-induced transparency, in the thinnest targets investigated, limits the velocity of the critical surface, and thus the e ff ectiveness of radiation pressure acceleration

Perspectives on laser-plasma physics in the relativistic transparency regime

With the advent of multi-petawatt lasers, the relativistic transparency regime of laser-plasma interactions becomes readily accessible for near-solid density targets. Initially opaque targets that undergo relativistic self-induced transparency (RSIT) have already shown to result in promising particle acceleration and radiation generation mechanisms, as well as relativistic optical and photonics phenomena that modify the spatial, temporal, spectral and polarization properties of the laser pulse itself. At the maximum laser intensities currently available, this opaque-to-RSIT transition regime can be achieved through ultrafast ionization, heating and expansion of initially ultrathin foil targets. Here, we review findings from our programme of work exploring this regime experimentally and numerically, including changes to the laser energy absorption, mechanisms for laser-driven particle acceleration and the generation of a relativistic plasma aperture. New physics induced by this aperture, such as the production of intense light with higher order spatial modes and higher harmonics, and spatially-structured and temporally-varying polarization states, is summarized. Prospects for exploring the physics of the RSIT regime with higher intensity and high repetition rate lasers, including expected new phenomena such as high-field effects and the application of new techniques such as machine learning, are also discussed; outlining directions for the future development of this promising laser-plasma interaction regime

Appropriate disclosure of a diagnosis of dementia : identifying the key behaviours of 'best practice'

Background: Despite growing evidence that many people with dementia want to know their diagnosis, there is wide variation in attitudes of professionals towards disclosure. The disclosure of the diagnosis of dementia is increasingly recognised as being a process rather than a one-off behaviour. However, the different behaviours that contribute to this process have not been comprehensively defined. No intervention studies to improve diagnostic disclosure in dementia have been reported to date. As part of a larger study to develop an intervention to promote appropriate disclosure, we sought to identify important disclosure behaviours and explore whether supplementing a literature review with other methods would result in the identification of new behaviours. Methods: To identify a comprehensive list of behaviours in disclosure we conducted a literature review, interviewed people with dementia and informal carers, and used a consensus process involving health and social care professionals. Content analysis of the full list of behaviours was carried out. Results: Interviews were conducted with four people with dementia and six informal carers. Eight health and social care professionals took part in the consensus panel. From the interviews, consensus panel and literature review 220 behaviours were elicited, with 109 behaviours over-lapping. The interviews and consensus panel elicited 27 behaviours supplementary to the review. Those from the interviews appeared to be self-evident but highlighted deficiencies in current practice and from the panel focused largely on balancing the needs of people with dementia and family members. Behaviours were grouped into eight categories: preparing for disclosure; integrating family members; exploring the patient's perspective; disclosing the diagnosis; responding to patient reactions; focusing on quality of life and well-being; planning for the future; and communicating effectively. Conclusion: This exercise has highlighted the complexity of the process of disclosing a diagnosis of dementia in an appropriate manner. It confirms that many of the behaviours identified in the literature (often based on professional opinion rather than empirical evidence) also resonate with people with dementia and informal carers. The presence of contradictory behaviours emphasises the need to tailor the process of disclosure to individual patients and carers. Our combined methods may be relevant to other efforts to identify and define complex clinical practices for further study.This project is funded by UK Medical Research Council, Grant reference number G0300999

Influence of laser polarization on collective electron dynamics in ultraintense laser-foil interactions

The collective response of electrons in an ultrathin foil target irradiated by an ultraintense laser pulse is investigated experimentally and via 3D particle-in-cell simulations. It is shown that if the target is sufficiently thin that the laser induces significant radiation pressure, but not thin enough to become relativistically transparent to the laser light, the resulting relativistic electron beam is elliptical, with the major axis of the ellipse directed along the laser polarization axis. When the target thickness is decreased such that it becomes relativistically transparent early in the interaction with the laser pulse, diffraction of the transmitted laser light occurs through a so called 'relativistic plasma aperture', inducing structure in the spatial-intensity profile of the beam of energetic electrons. It is shown that the electron beam profile can be modified by variation of the target thickness and degree of ellipticity in the laser polarization

Towards optical polarization control of laser-driven proton acceleration in foils undergoing relativistic transparency

Control of the collective response of plasma particles to intense laser light is intrinsic to relativistic optics, the development of compact laser-driven particle and radiation sources, as well as investigations of some laboratory astrophysics phenomena. We recently demonstrated that a relativistic plasma aperture produced in an ultra-thin foil at the focus of intense laser radiation can induce diffraction, enabling polarization-based control of the collective motion of plasma electrons. Here we show that under these conditions the electron dynamics are mapped into the beam of protons accelerated via strong charge-separation-induced electrostatic fields. It is demonstrated experimentally and numerically via 3D particle-in-cell simulations that the degree of ellipticity of the laser polarization strongly influences the spatial-intensity distribution of the beam of multi-MeV protons. The influence on both sheath accelerated and radiation pressure accelerated protons is investigated. This approach opens up new routes to control laser-driven ion sources

To what extent can behaviour change techniques be identified within an adaptable implementation package for primary care? A prospective directed content analysis

Interpreting evaluations of complex interventions can be difficult without sufficient description of key intervention content. We aimed to develop an implementation package for primary care which could be delivered using typically available resources and could be adapted to target determinants of behaviour for each of four quality indicators: diabetes control, blood pressure control, anticoagulation for atrial fibrillation and risky prescribing. We describe the development and prospective verification of behaviour change techniques (BCTs) embedded within the adaptable implementation packages

Development of Focusing Plasma Mirrors for Ultraintense Laser-Driven Particle and Radiation Sources

Increasing the peak intensity to which high power laser pulses are focused can open up new regimes of laser-plasma interactions, resulting in the acceleration of ions to higher energies and more efficient generation of energetic photons. Low f-number focusing plasma mirrors, which re-image and demagnify the laser focus, provide an attractive approach to producing higher intensities, without requiring significant changes to the laser system. They are small, enhance the pulse intensity contrast and eliminate the requirement to expose expensive optics directly to target debris. We report on progress made in a programme of work to design, manufacture and optimise ellipsoidal focusing plasma mirrors. Different approaches to manufacturing these innovative optics are described, and the results of characterisation tests are presented. The procedure developed to align the optics is outlined, together with initial results from their use with a petawatt-level laser