152 research outputs found

    Optical carrier wave shocking: detection and dispersion

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    Carrier wave shocking is studied using the Pseudo-Spectral Spatial Domain (PSSD) technique. We describe the shock detection diagnostics necessary for this numerical study, and verify them against theoretical shocking predictions for the dispersionless case. These predictions show Carrier Envelope Phase (CEP) and pulse bandwidth sensitivity in the single-cycle regime. The flexible dispersion management offered by PSSD enables us to independently control the linear and nonlinear dispersion. Customized dispersion profiles allow us to analyze the development of both carrier self-steepening and shocks. The results exhibit a marked asymmetry between normal and anomalous dispersion, both in the limits of the shocking regime and in the (near) shocked pulse waveforms. Combining these insights, we offer some suggestions on how carrier shocking (or at least extreme self-steepening) might be realised experimentally.Comment: 9 page

    Uncomfortable truths - teamworking under lean in the UK

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    A recent contribution in this journal – Procter, S. and Radnor, Z. (2014) ‘Teamworking under Lean in UK public services: lean teams and team targets in Her Majesty’s Revenue and Customs (HMRC)’ International Journal of Human Resource Management, 25:21, 2978–2995 – provides an account of teamworking in the UK Civil Service, specifically Her Majesty’s Revenue and Customs (HMRC), focused on the relationship between recently implemented lean work organisation and teams and teamworking. Procter and Radnor claim in this work that it delivers a ‘more nuanced’ analysis of lean in this government department and, it follows, of the lean phenomenon more generally. Our riposte critiques their article on several grounds. It suffers from problems of logic and construction, conceptual confusion and definitional imprecision. Methodological difficulties and inconsistent evidence contribute additionally to analytical weakness. Included in our response are empirical findings on teamworking at HMRC that challenge Procter and Radnor’s evidential basis and further reveal the shortcomings of their interpretation

    Carrier-wave steepened pulses and gradient-gated high-order harmonic generation using linear ramp waveforms

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    We show how to optimize the process of high-harmonic generation (HHG) by gating the interaction using the field gradient of a driving pulse with a linear ramp waveform. Since maximized field gradients are efficiently generated by self-steepening processes, we first present a generalized theory of optical carrier-wave self-steepened (CSS) pulses. This goes beyond existing treatments, which only consider third-order nonlinearity, and has the advantage of describing pulses whose wave forms have a range of symmetry properties. Although a fertile field for theoretical work, CSS pulses are difficult to realize experimentally because of the deleterious effect of dispersion. We therefore consider synthesizing CSS-like profiles using a suitably phased sub-set of the harmonics present in a true CSS wave form. Using standard theoretical models of HHG, we show that the presence of gradient-maximized regions on the wave forms can raise the spectral cut-off and so yield shorter attosecond pulses. We study how the quality of the attosecond bursts created by spectral filtering depends on the number of harmonics included in the driving pulse.Comment: 8 pages, 10 figures; with appendix not present in published versio

    Positional training demands in the English Premier League and EnglishChampionship. A longitudinal study across consecutive seasons

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    The aims of this study were to: compare training loads between the English Premier League (EPL) and English Championship League (ECL) and examine differences between playing positions. Forty-six 1st team players from the same club participated in the study. GPS metrics were obtained during all EPL and ECL training sessions across four consecutive seasons, 2019–20 to 2022–23. The study team was promoted from the ECL at the end of season 2020–21. There was a significant interaction effect between position and league for all GPS metrics (p < 0.001; η2 = 0.001–0.003), except for relative high-speed running (HSR) distance, sprint distance, and sprint efforts (p > 0.05). A significant main effect for league for all GPS metrics (p < 0.001; η2 = 0.001–0.009) was found, with EPL training sessions resulting in greater total distance per minute, HSR distance per minute, high metabolic load distance (HMLD) per minute, number of HML efforts, accelerations, and decelerations per minute compared to training in the ECL (p < 0.001; d = 0.061–0.224). For position, a significant main effect for all GPS metrics (p < 0.001; η2 = 0.001–0.005) was observed. Centre midfielders covered more distance per minute than all other positions (p < 0.001, d = 0.040–0.167). In conclusion, higher training values in the EPL were evident, except for centre forwards, providing some guidance on the differing positional physical demands that may support coaches and practitioners to design position-specific drills incorporating physical and technical/tactical strategiesinfo:eu-repo/semantics/publishedVersio
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