Single-ionization of helium at Ti:sapphire wavelengths: rates and scaling laws

We present a numerical and theoretical study of intense-field single-electron ionization of helium at 390 nm and 780 nm. Accurate ionization rates (over an intensity range of (0.175-34) X10^14 W/ cm^2 at 390 nm, and (0.275 - 14.4) X 10^14 W /cm^2 at 780 nm) are obtained from full-dimensionality integrations of the time-dependent helium-laser Schroedinger equation. We show that the power law of lowest order perturbation theory, modified with a ponderomotive-shifted ionization potential, is capable of modelling the ionization rates over an intensity range that extends up to two orders of magnitude higher than that applicable to perturbation theory alone. Writing the modified perturbation theory in terms of scaled wavelength and intensity variables, we obtain to first approximation a single ionization law for both the 390 nm and 780 nm cases. To model the data in the high intensity limit as well as in the low, a new function is introduced for the rate. This function has, in part, a resemblance to that derived from tunnelling theory but, importantly, retains the correct frequency-dependence and scaling behaviour derived from the perturbative-like models at lower intensities. Comparison with the predictions of classical ADK tunnelling theory confirms that ADK performs poorly in the frequency and intensity domain treated here.

Parent-offspring conflict and motivational control of brooding in an amphipod (Crustacea)

Models of parent - offspring conflict concerning levels of caregiving centre on conflict resolution by offspring control, compromise or offspring 'honest signalling' that parents use to maximize their own fitness. Recent empirical studies on motivational control of parental feeding of offspring are interpreted as supporting the latter model. Here, we examine parental care in an amphipod, Crangonyx pseudogracilis, which directs care to embryos in a brood pouch. Embryo removal and transplantation elucidated causal factors that determine levels of caregiving. In the short-term, females with all embryos removed reduced care activities, but partial embryo removal did not affect caregiving, evidence of 'unshared' parental care. In the long-term, females with all embryos removed ceased care. Thus, females have a maternal state that is maintained by stimuli from offspring. Transplantation of early/late stage embryos among females originally carrying early/late stage embryos revealed that stimuli from embryos indicate their age-dependent needs, but only modify caregiving within the constraints of a changing endogenous maternal state. Thus, we demonstrate that mothers and offspring share motivational control of care. However, we highlight the inappropriate use of motivational data in reaching conclusions about the resolution of parent - offspring conflict.

Conflict, Regulation and Marginalisation in the North of Ireland: The Experiences of Children and Young People

Based on primary research and consultations conducted over the last four years in the north of Ireland, this article considers the lives and experiences of children and young people in communities where the legacy of conflict and economic deprivation are most marked. It explores the reality of differential policing in communities where paramilitaries filled the policing deficit during the Conflict through informal 'justice' and punishment beatings. Finally, it considers the potential for change in a climate increasingly hostile towards children and young people, and the realisation of their rights.

‘Risk, Politics and the ‘Scientification’ of Political Judgement: Prisoner Release and Conflict Transformation in Northern Ireland’

Drawing on research in Northern Ireland into the process of release under the Belfast/Good Friday Agreement, this article explores the identification and classification of risk in relation to prisoners released early under the Sentences (NI) Act. The main argument is that conflict, post-conflict and transitional conditions expose more starkly the political underpinnings of risk-management strategy and the article demonstrates the particular variant of Politicized Risk Assessment (PRA) recently used in the release of prisoners in Northern Ireland

Placing political economy: organising opposition to free trade before the abolition of the Corn Laws

The unfurling of global capitalism – and its attendant effects – has long been fertile intellectual terrain for geographers. But whilst studies of the processes and mechanisms of globalisation undoubtedly assume a talismanic importance in the discipline, geographers, with few exceptions, have left examinations of early economic liberalism to historians. One such critically important episode in the evolution of the liberal economic project was the repeal of the so-called 'Corn Laws' in 1846. Whilst the precise impact of the Manchester-based Anti-Corn Law League (ACLL) continues to be a matter of conjecture, Eric Sheppard has asserted that their particular take on political economy managed to assume a 'truth-like status' and worldwide universality. But the ACLL's campaign represents only one, albeit decisive, stage in the long intellectual and practical struggle between 'protectionists' and the disciples of free trade. Studies of the non-'Manchester' components have tended to focus squarely upon national politics. This paper examines a pivotal attempt in 1838 by Lord Melbourne's Government to experiment with the effective elimination of import duties on fresh fruit. Unlike most agricultural commodities, table fruit was produced in a tightly defined area, thus allowing the Government's experiment to play out, in theory, without national political fallout. Whilst the Government's clandestine actions left little time for a concerted opposition to develop, Kentish fruit growers soon organised. A formidable lobby was forged that drew wide local support yet also evolved beyond the original 'epistemic community'. Whilst the coalition failed in their efforts to reintroduce protective duties, their actions allow us to see how protectionist ideologies and policies were vivified through practices at many different spatial scales and to better understand the complex spatiality of protectionist takes on political economy. Their campaign also changed – at least in the short term – the course of British mercantile policy.

Protest practice and (tree) cultures of conflict: understanding the spaces of ‘tree maiming’ in eighteenth- and early nineteenth-century England

Developing understandings of protest and cultures of resistance has been a central theme of the 'new' cultural geography of the 1990s and 2000s. But whilst geographers of the here and now have been highly sensitive to the importance of acts of protest which occur outside of the context of broader social movements, geographers concerned with past protests have tended to focus overwhelmingly upon either understanding the development of social movements or highly specific place-based studies. Through a focus upon the hitherto ignored practice of 'tree maiming', this paper demonstrates not only the value of examining specific protest practices in helping to better understand the complexity of conflict, but also how in periods of acute socio-economic change the evolving relationship between humans and the non-human – in this case trees – is a central discourse to the protest practices of the poor. Such attacks often involved complex cultural understandings about the ways in which trees should – and should not – be socially enrolled.