Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources

Laser-driven plasma accelerators can generate accelerating gradients three orders of magnitude larger than radio-frequency accelerators and have achieved beam energies above 1 GeV in centimetre long stages. However, the pulse repetition rate and wall-plug efficiency of plasma accelerators is limited by the driving laser to less than approximately 1 Hz and 0.1% respectively. Here we investigate the prospects for exciting the plasma wave with trains of low-energy laser pulses rather than a single high-energy pulse. Resonantly exciting the wakefield in this way would enable the use of different technologies, such as fibre or thin-disc lasers, which are able to operate at multi-kilohertz pulse repetition rates and with wall-plug efficiencies two orders of magnitude higher than current laser systems. We outline the parameters of efficient, GeV-scale, 10-kHz plasma accelerators and show that they could drive compact X-ray sources with average photon fluxes comparable to those of third-generation light source but with significantly improved temporal resolution. Likewise FEL operation could be driven with comparable peak power but with significantly larger repetition rates than extant FELs

On Torsion-Free Crawley Groups

The notion of a Crawley p-group is well known in Abelian group theory. In this present work, a corresponding concept is introduced for torsion-free groups. The principal result, which uses the set-theoretic notions of the diamond and Martin’s axiom, establishes an independence result for N1-free Crawley groups

Laserwire at the Accelerator Test Facility 2 with Sub-Micrometre Resolution

A laserwire transverse electron beam size measurement system has been developed and operated at the Accelerator Test Facility 2 (ATF2) at KEK. Special electron beam optics were developed to create an approximately 1 x 100 {\mu}m (vertical x horizontal) electron beam at the laserwire location, which was profiled using a 150 mJ, 71 ps laser pulse with a wavelength of 532 nm. The precise characterisation of the laser propagation allows the non-Gaussian transverse profiles of the electron beam caused by the laser divergence to be deconvolved. A minimum vertical electron beam size of 1.07 ${\pm}$ 0.06 (stat.) ${\pm}$ 0.05 (sys.) {\mu}m was measured. A vertically focussing quadrupole just before the laserwire was varied whilst making laserwire measurements and the projected vertical emittance was measured to be 82.56 ${\pm}$ 3.04 pm rad.Comment: 17 pages, 26 figures, submitted to Phys. Rev. ST Accel. Beam

An intervention to improve outcomes of falls in dementia: the DIFRID mixed-methods feasibility study:A mixed methods study to develop and assess the feasibility of the DIFRID intervention

Background : Fall-related injuries are a significant cause of morbidity and mortality in people with dementia (PWD). There is presently little evidence to guide the management of such injuries, and yet there are potentially substantial benefits to be gained if the outcome of these injuries could be improved. This study aimed to design an appropriate new healthcare intervention for PWD following a fall and to assess the feasibility of its delivery in the UK National Health Service. Objective (s): To determine whether it is possible to design an intervention to improve outcomes of falls in dementia; to investigate the feasibility and acceptability of the DIFRID intervention; to investigate the feasibility of a future randomised controlled trial (RCT) and data collection tools needed to evaluate the effectiveness and efficiency of the DIFRID intervention. Design : Mixed-methods feasibility study. Methods : A systematic review (using Cochrane methodology) and realist review (using RAMESES methodology) explored the existing evidence base and developed programme theories. Searches were carried out in Nov 2015 (updated Jan 2018) for effectiveness studies and August 2016 for economic studies. A prospective observational study identified service use via participant diary completion. Qualitative methods (semi-structured interviews, focus groups, and observation) were used to explore: current practice; stakeholder perspectives of the health and social care needs of PWD following a fall; ideas for intervention; and barriers and facilitators to change. Each of these datasets informed intervention development, via Delphi consensus methods. Finally, a single-arm feasibility study with embedded process evaluation was conducted. Setting : Community. Participants : PWD presenting with falls needing healthcare attention in each setting at 3 sites and their carers. Professionals delivering the intervention, responsible for training and supervision and members of the intervention team. Professionals responsible for approaching and recruiting participants. Interventions: A complex multidisciplinary therapy intervention. Physiotherapists, occupational therapists, and support workers delivered up to 22 sessions of tailored activities in the PWD’s home or local area over a period of 12 weeks. Main outcome measures: Assessment of feasibility of study procedures; assessment of the acceptability, feasibility and fidelity of intervention components; assessment of suitability and acceptability of outcome measures for PWD and carers (number of falls; quality of life; fear of falling; activities of daily living; goal setting; health utilisation; carer burden). Results : A multidisciplinary intervention delivered in PWDs’ own homes was designed based on qualitative work, realist review and recommendations of the consensus panel. The intervention was delivered to 11 PWD. The study suggested that the intervention is both feasible and acceptable to stakeholders. A number of modifications was recommended to address some of the issues arising during feasibility testing. Measurement of outcome measures was successful. Limitations : Recruitment to the feasibility study was lower than expected and therefore the intervention needs to be tested with a larger number of PWD. Conclusions : The study has highlighted the feasibility of delivering a creative, tailored, individual approach to intervention for PWD following a fall. Although the intervention required greater investment of time than usual practice, many staff valued the opportunity to work more closely with PWD and carers. Future work : We conclude that further research is now needed to refine this intervention in the context of a pilot randomised controlled trial

Science and Film-making

The essay reviews the literature, mostly historical, on the relationship between science and film-making, with a focus on the science documentary. It then discusses the circumstances of the emergence of the wildlife making-of documentary genre. The thesis examined here is that since the early days of cinema, film-making has evolved from being subordinate to science, to being an equal partner in the production of knowledge, controlled by non-scientists

Density-dependence of functional development in spiking cortical networks grown in vitro

During development, the mammalian brain differentiates into specialized regions with distinct functional abilities. While many factors contribute to functional specialization, we explore the effect of neuronal density on the development of neuronal interactions in vitro. Two types of cortical networks, dense and sparse, with 50,000 and 12,000 total cells respectively, are studied. Activation graphs that represent pairwise neuronal interactions are constructed using a competitive first response model. These graphs reveal that, during development in vitro, dense networks form activation connections earlier than sparse networks. Link entropy analysis of dense net- work activation graphs suggests that the majority of connections between electrodes are reciprocal in nature. Information theoretic measures reveal that early functional information interactions (among 3 cells) are synergetic in both dense and sparse networks. However, during later stages of development, previously synergetic relationships become primarily redundant in dense, but not in sparse networks. Large link entropy values in the activation graph are related to the domination of redundant ensembles in late stages of development in dense networks. Results demonstrate differences between dense and sparse networks in terms of informational groups, pairwise relationships, and activation graphs. These differences suggest that variations in cell density may result in different functional specialization of nervous system tissue in vivo.Comment: 10 pages, 7 figure

Process evaluation of a university residence-based SARS-CoV-2 testing programme in the UK

Background Regular testing for SARS-CoV-2 is an important strategy for controlling virus outbreaks on university campuses during the COVID-19 pandemic but testing participation can be low. The Residence-Based Testing Participation Pilot (RB-TPP) was a novel 4-week intervention implemented at two student residences on a UK university campus, aiming to increase asymptomatic testing frequency and normalise university life through relaxed social restrictions onsite. Methods Mixed-methods process evaluation determined whether RB-TPP was implemented as planned and identified implementation barriers and facilitators. Data were collected from meeting records, university students (online survey: n = 152; focus groups: n = 30), and staff (interviews, n = 13). Barriers and facilitators to implementation were mapped to the ‘Capability, Opportunity, Motivation-Behaviour’ (COM-B) behaviour change framework. Results Uptake was high (n = 464 students opted-in; 98% of those living onsite). Implementation was broadly as planned, with adjustments due to national escalation of the COVID-19 Delta variant. Majority engaged in testing (88%); 46% (52% of testers) were fully compliant with pre-determined testing frequency. Most felt positively towards relaxed social distancing (97.9%). Implementation was facilitated by convenience and efficiency of testing and reduced negative impacts of isolation through opportunities for students to socialise. Barriers to implementation were mixed-messages about the rules, ambivalent attitudes, and lack of adherence to COVID-19 protective measures in the minority. Conclusions This is the first process evaluation of the implementation of asymptomatic SARS-CoV-2 testing in university residences. Testing participation increased and student mental wellbeing improved. Rapid adaptions to the changing pandemic context generated complexity and challenge. Findings have global relevance for outbreak prevention and management strategies in higher education settings. Key messages • Delivery of asymptomatic SARS-CoV-2 testing and relaxation of social distancing within residences led to high rates of testing participation and benefits for student mental wellbeing. • This is the first process evaluation of the implementation of asymptomatic SARS-CoV-2 testing in university residences with global relevance for outbreak prevention in higher education settings

Lung cancer diagnosed following an emergency admission: exploring patient and carer perspectives on delay in seeking help

Purpose Compared to others, patients diagnosed with lung cancer following an emergency, unplanned admission to hospital (DFEA) have more advanced disease and poorer prognosis. Little is known about DFEA patients’ beliefs about cancer and its symptoms or about their help-seeking behaviours prior to admission. Methods As part of a larger single-centre, prospective mixed-methods study conducted in one University hospital, we undertook qualitative interviews with patients DFEA and their carers to obtain their understanding of symptoms and experiences of trying to access healthcare services before admission to hospital. Interviews were recorded and transcribed. Framework analysis was employed. Results Thirteen patients and 10 carers plus 3 bereaved carers took part in interviews. Three patient/carer dyads were interviewed together. Participants spoke about their symptoms and why they did not seek help sooner. They described complex and nuanced experiences. Some (n = 12) had what they recalled as the wrong symptoms for lung cancer and attributed them either to a pre-existing condition or to ageing. In other cases (n = 9), patients or carers realised with hindsight that their symptoms were signs of lung cancer, but at the time had made other attributions to account for them. In some cases (n = 3), a sudden onset of symptoms was reported. Some GPs (n = 6) were also reported to have made incorrect attributions about cause. Conclusion Late diagnosis meant that patients DFEA needed palliative support sooner after diagnosis than patients not DFEA. Professionals and lay people interpret health and illness experiences differently

High-gradient plasma and laser accelerators

Novel high-gradient accelerators have demonstrated acceleration of electrons and positrons with electric field strengths of 1 to > 100 GeV/m. This is about 10 to 1000 times higher than achieved in RF-based accelerators, and as such they have the potential to overcome the limitations associated with RF cavities. Plasma-based accelerators have produced multi-GeV bunches with parameters approaching those suitable for a linear collider. These accelerators offer the prospect of near term, compact and cost-effective particle physics experiments that provide new physics possibilities supporting precision studies and the search for new particles. The expert panel has defined a long term R&D roadmap towards a compact collider with attractive intermediate experiments and studies. A delivery plan for the required R&D has been developed and includes work packages, deliverables, a minimal plan, connections to ongoing projects and an aspirational plan