Chirped pulse Raman amplification in warm plasma: towards controlling saturation

Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10's - 100's fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies.close0

Progress Towards Laser Wakefield Acceleration and Applications at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA)

Abstract Laser wakefield accelerators (LWFAs) are promising sources of high brightness particle and radiation beams with many possible applications, ranging from scientific research to medicine, industry and border security. The Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) is a university-based facility employing the use of two high-power, ultrashort pulse lasers to advance research, development and application of laser-plasma accelerators. Here we report on recent advancements in LWFA research at SCAPA and upcoming research programmes to demonstrate proof-of-concept applications of the LWFA.</jats:p

'It makes sense and it works': maternity care providers' perspectives on the feasibility of a group antenatal care model (Pregnancy Circles)

Aim To test the feasibility of introducing a group antenatal care initiative (Pregnancy Circles) in an area with high levels of social deprivation and cultural diversity by exploring the views and experiences of midwives and other maternity care providers in the locality before and after the implementation of a test run of the group model. Design (i) Pre-implementation semi-structured interviews with local stakeholders. (ii) Post-implementation informal and semi-structured interviews and a reflective workshop with facilitating midwives, and semi-structured interviews with maternity managers and commissioners. Data were organised around three core themes of organisational readiness, the acceptability of the model and its impact on midwifery practice, and analyzed thematically. Setting A large inner-city National Health Service Trust in the United Kingdom. Participants Sixteen stakeholders were interviewed prior to, and ten after, the group model was implemented. Feedback was also obtained from a further nine midwives and one student midwife who facilitated the Pregnancy Circles. Intervention Four Pregnancy Circles in community settings. Women with pregnancies of similar gestation were brought together for antenatal care incorporating information sharing and peer support. Women undertook their own blood pressure and urine checks, and had brief individual midwifery checks in the group space. Findings Dissatisfaction with current practice fuelled organisational readiness and the intervention was both possible and acceptable in the host setting. A perceived lack of privacy in a group setting, the ramifications of devolving blood pressure and urine checks to women, and the involvement of partners in sessions were identified as sticking points. Facilitating midwives need to be adequately supported and trained in group facilitation. Midwives derived accomplishment and job satisfaction from working in this way, and considered that it empowered women and enhanced care. Key conclusions Participants reported widespread dissatisfaction with current care provision. Pregnancy Circles were experienced as a safe environment in which to provide care, and one that enabled midwives to build meaningful relationships with women. Implications for practice Pre-registration education inadequately prepared midwives for group care. Addressing sticking points and securing management support for Pregnancy Circles is vital to sustain participation in this model of care

Better together: A qualitative exploration of women’s perceptions and experiences of group antenatal care

Problem Childbearing women from socio-economically disadvantaged communities and minority ethnic groups are less likely to access antenatal care and experience more adverse pregnancy outcomes. Background Group antenatal care aims to facilitate information sharing and social support. It is associated with higher rates of attendance and improved health outcomes. Aims To assess the acceptability of a bespoke model of group antenatal care (Pregnancy Circles) in an inner city community in England, understand how the model affects women’s experiences of pregnancy and antenatal care, and inform further development and testing of the model. Methods A two-stage qualitative study comprising focus groups with twenty six local women, followed by the implementation of four Pregnancy Circles attended by twenty four women, which were evaluated using observations, focus groups and semi-structured interviews with participants. Data were analysed thematically. Findings Pregnancy Circles offered an appealing alternative to standard antenatal care and functioned as an instrument of empowerment, mediated through increased learning and knowledge sharing, active participation in care and peer and professional relationship building. Multiparous women and women from diverse cultures sharing their experiences during Circle sessions was particularly valued. Participants had mixed views about including partners in the sessions. Conclusions Group antenatal care, in the form of Pregnancy Circles, is acceptable to women and appears to enhance their experiences of pregnancy. Further work needs to be done both to test the findings in larger, quantitative studies and to find a model of care that is acceptable to women and their partners. Abbreviations FG, focus group; gANC, group antenatal care; REACH, research for equitable antenatal care and health; UK, United Kingdom; USA, United States of Americ

Better together: a qualitative exploration of women’s perceptions and experiences of group antenatal care using focus groups and interviews

Problem. Childbearing women from socio-economically disadvantaged communities and minority ethnic groups are less likely to access antenatal care and experience more adverse pregnancy outcomes. Background. Group antenatal care aims to facilitate information sharing and social support. It is associated with higher rates of attendance and improved health outcomes. Aims. To assess the acceptability of a bespoke model of group antenatal care (Pregnancy Circles) in an inner city community in England, understand how the model affects women’s experiences of pregnancy and antenatal care, and inform further development and testing of the model. Methods. A two-stage qualitative study comprising focus groups with twenty six local women, followed by the implementation of four Pregnancy Circles attended by twenty four women, which were evaluated using observations, focus groups and semi-structured interviews with participants. Data were analysed thematically. Findings. Pregnancy Circles offered an appealing alternative to standard antenatal care and functioned as an instrument of empowerment, mediated through increased learning and knowledge sharing, active participation in care and peer and professional relationship building. Multiparous women and women from diverse cultures sharing their experiences during Circle sessions was particularly valued. Participants had mixed views about including partners in the sessions. Conclusions. Group antenatal care, in the form of Pregnancy Circles, is acceptable to women and appears to enhance their experiences of pregnancy. Further work needs to be done both to test the findings in larger, quantitative studies and to find a model of care that is acceptable to women and their partners

How do you say ‘hello’? Personality impressions from brief novel voices

On hearing a novel voice, listeners readily form personality impressions of that speaker. Accurate or not, these impressions are known to affect subsequent interactions; yet the underlying psychological and acoustical bases remain poorly understood. Furthermore, hitherto studies have focussed on extended speech as opposed to analysing the instantaneous impressions we obtain from first experience. In this paper, through a mass online rating experiment, 320 participants rated 64 sub-second vocal utterances of the word ‘hello’ on one of 10 personality traits. We show that: (1) personality judgements of brief utterances from unfamiliar speakers are consistent across listeners; (2) a two-dimensional ‘social voice space’ with axes mapping Valence (Trust, Likeability) and Dominance, each driven by differing combinations of vocal acoustics, adequately summarises ratings in both male and female voices; and (3) a positive combination of Valence and Dominance results in increased perceived male vocal Attractiveness, whereas perceived female vocal Attractiveness is largely controlled by increasing Valence. Results are discussed in relation to the rapid evaluation of personality and, in turn, the intent of others, as being driven by survival mechanisms via approach or avoidance behaviours. These findings provide empirical bases for predicting personality impressions from acoustical analyses of short utterances and for generating desired personality impressions in artificial voices

A mathematical framework for critical transitions: normal forms, variance and applications

Critical transitions occur in a wide variety of applications including mathematical biology, climate change, human physiology and economics. Therefore it is highly desirable to find early-warning signs. We show that it is possible to classify critical transitions by using bifurcation theory and normal forms in the singular limit. Based on this elementary classification, we analyze stochastic fluctuations and calculate scaling laws of the variance of stochastic sample paths near critical transitions for fast subsystem bifurcations up to codimension two. The theory is applied to several models: the Stommel-Cessi box model for the thermohaline circulation from geoscience, an epidemic-spreading model on an adaptive network, an activator-inhibitor switch from systems biology, a predator-prey system from ecology and to the Euler buckling problem from classical mechanics. For the Stommel-Cessi model we compare different detrending techniques to calculate early-warning signs. In the epidemics model we show that link densities could be better variables for prediction than population densities. The activator-inhibitor switch demonstrates effects in three time-scale systems and points out that excitable cells and molecular units have information for subthreshold prediction. In the predator-prey model explosive population growth near a codimension two bifurcation is investigated and we show that early-warnings from normal forms can be misleading in this context. In the biomechanical model we demonstrate that early-warning signs for buckling depend crucially on the control strategy near the instability which illustrates the effect of multiplicative noise.Comment: minor corrections to previous versio

Stereotyping of medical disability claimants' communication behaviour by physicians: towards more focused education for social insurance physicians

Background: Physicians who hold medical disability assessment interviews (social insurance physicians) are probably influenced by stereotypes of claimants, especially because they have limited time available and they have to make complicated decisions. Because little is known about the influences of stereotyping on assessment interviews, the objectives of this paper were to qualitatively investigate: (1) the content of stereotypes used to classify claimants with regard to the way in which they communicate; (2) the origins of such stereotypes; (3) the advantages and disadvantages of stereotyping in assessment interviews; and (4) how social insurance physicians minimise the undesirable influences of negative stereotyping. Methods: Data were collected during three focus group meetings with social insurance physicians who hold medical disability assessment interviews with sick-listed employees (i.e. claimants). The participants also completed a questionnaire about demographic characteristics. The data were qualitatively analysed in Atlas.ti in four steps, according to the grounded theory and the principle of constant comparison. Results: A total of 22 social insurance physicians participated. Based on their responses, a claimant's communication was classified with regard to the degree of respect and acceptance in the physician-claimant relationship, and the degree of dominance. Most of the social insurance physicians reported that they classify claimants in general groups, and use these classifications to adapt their own communication behaviour. Moreover, the social insurance physicians revealed that their stereotypes originate from information in the claimants' files and first impressions. The main advantages of stereotyping were that this provides a framework for the assessment interview, it can save time, and it is interesting to check whether the stereotype is correct. Disadvantages of stereotyping were that the stereotypes often prove incorrect, they do not give the complete picture, and the claimant's behaviour changes constantly. Social insurance physicians try to minimise the undesirable influences of stereotypes by being aware of counter transference, making formal assessments, staying neutral to the best of their ability, and being compassionate. Conclusions: We concluded that social insurance physicians adapt their communication style to the degree of respect and dominance of claimants in the physician-claimant relationship, but they try to minimise the undesirable influences of stereotypes in assessment interviews. It is recommended that this issue should be addressed in communication skills trainin