37 research outputs found

    Generation and acceleration of electron bunches from a plasma photocathode

    Get PDF
    Plasma waves generated in the wake of intense, relativistic laser1,2 or particle beams3,4 can accelerate electron bunches to gigaelectronvolt energies in centimetre-scale distances. This allows the realization of compact accelerators with emerging applications ranging from modern light sources such as the free-electron laser to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre wakefields can accelerate witness electron bunches that are either externally injected5,6 or captured from the background plasma7,8. Here we demonstrate optically triggered injection9–11 and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This ‘plasma photocathode’ decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical11 density down-ramp injection12–16 and is an important step towards the generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness17. This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultrahigh-brightness beams

    The fate of children with microdeletion 22q11.2 syndrome and congenital heart defect: clinical course and cardiac outcome

    Full text link
    BACKGROUND: This study aimed to evaluate the cardiac outcome for children with microdeletion 22q11.2 and congenital heart defect (CHD). METHODS: A total of 49 consecutive children with 22q11.2 and CHD were retrospectively identified. The CHD consisted of tetralogy of Fallot and variances (n = 22), interrupted aortic arch (n = 10), ventricular septal defect (n = 8), truncus arteriosus (n = 6), and double aortic arch (n = 1). Extracardiac anomalies were present in 46 of 47 children. RESULTS: The median follow-up time was 8.5 years (range, 3 months to 23.5 years). Cardiac surgical repair was performed for 35 children, whereas 5 had palliative surgery, and 9 never underwent cardiac surgery. The median age at repair was 7.5 months (range, 2 days to 5 years). The mean hospital stay was 35 days (range, 7-204 days), and the intensive care unit stay was 15 days (range, 3-194 days). Significant postoperative complications occurred for 26 children (74%), and surgery for extracardiac malformations was required for 21 patients (43%). The overall mortality rate was 22% (11/49), with 1-year survival for 86% and 5-year survival for 80% of the patients. A total of 27 cardiac reinterventions were performed for 16 patients (46%) including 15 reoperations and 12 interventional catheterizations. Residual cardiac findings were present in 25 patients (71%) at the end of the follow-up period. CONCLUSIONS: Children with microdeletion 22q11.2 and CHD are at high risk for mortality and morbidity, as determined by both the severity of the cardiac lesions and the extracardiac anomalies associated with the microdeletion

    Mapping the Relationship Among Political Ideology, CSR Mindset, and CSR Strategy: A Contingency Perspective Applied to Chinese Managers

    Get PDF
    The literature on antecedents of corporate social responsibility (CSR) strategies of firms has been predominately content driven. Informed by the managerial sense-making process perspective, we develop a contingency theoretical framework explaining how political ideology of managers affects the choice of CSR strategy for their firms through their CSR mindset. We also explain to what extent the outcome of this process is shaped by the firm’s internal institutional arrangements and external factors impacting on the firm. We develop and test several hypotheses using data collected from 129 Chinese managers. The results show that managers with a stronger socialist ideology are likely to develop a mindset favouring CSR, which induces the adoption of a proactive CSR strategy. The CSR mindset mediates the link between socialist ideology and CSR strategy. The strength of the relationship between the CSR mindset and the choice of CSR strategy is moderated by customer response to CSR, industry competition, the role of government, and CSR-related managerial incentives

    Comments on the mechanisms of action of radiation protective agents: basis components and their polyvalence

    No full text
    corecore