Electron-impact excitation of FeII - Collision strengths and effective collision strengths for low-lying fine-structure forbidden transitions

Context. Absorption or emission lines of Fe II are observed in many astrophysical spectra and accurate atomic data are required to interpret these lines. The calculation of electron-impact excitation rates for transitions among even the lowest lying levels of Fe II is a formidable task for theoreticians.

Aims. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of Fe II for low-lying forbidden transitions among the lowest 16 fine-structure levels arising from the four LS states 3d(6)4s D-6(e), 3d(7) F-4(e), 3d(6)4s D-4(e), and 3d(7) P-4(e). The effective collision strengths are calculated for a wide range of electron temperatures of astrophysical importance from 30-100 000 K.

Methods. The parallel suite of Breit-Pauli codes are utilised to compute the collision cross sections for electron-impact excitation of Fe II and relativistic terms are included explicitly in both the target and the scattering approximation. 100 LS or 262-jj levels formed from the basis configurations 3d(6)4s, 3d(7), and 3d(6)4p were included in the wavefunction representation of the target, including all doublet, quartet, and sextet terms. Collision strengths for a total of 34191 individual transitions were computed.

Results. A detailed comparison is made with previous theoretical works and significant differences were found to occur in the effective collision strengths, particularly at low temperatures.

Studies into the effect of temperature on the impact of model particles in co-melt granulation

In co-melt granulation, collisions occur between the particles to be agglomerated and the binder material. Depending on the stage of granulation, the binder material can be in the solid or liquid phase. The outcome of these collisions controls the dynamics of the granulation process and the fundamental physics of the impacts are of interest. This paper examines the impact of glass beads (model particles) and solid Poly Ethylene Glycol (PEG) flakes on a substrate of PEG as the temperature of the PEG layer is increased from below its melting point to above it. While the layer is in the solid state, the result of the impact can be quantified by the coefficient of restitution. When the layer is in the liquid state, the impact can be quantified by the immersion behaviour. The results obtained show that the coefficient of restitution between either glass beads and PEG flakes and the PEG layer is strongly affected by temperatures. As the PEG layer approaches its melting point, the coefficient of restitution falls to zero. Once the temperature of the PEG layer exceeds the melting point, the impact is characterised by a transient maximum indentation and then rebound to an equilibrium position. These too are strongly dependent on temperature.

Shadow policing: the boundaries of community-based ‘policing’ in Northern Ireland

The intention of this article is to provide a structural and operational analysis of policing beyond the police in Northern Ireland. While the polity enjoys low levels of ‘officially’ recorded crime as part of its post-conflict status, little empirical analysis exists as to the epistemological roots of security production outside that of the Police Service of Northern Ireland. The empirical evidence presented seeks to establish that beyond more prominent analyses related to paramilitary ‘policing’, the country is in fact replete with a substantial reservoir of legitimate civil society policing – the collective mass of which contributes to policing, community safety and quality of life issues. While such non-state policing at the level of locale was recognised by the Independent Commission for Policing, structured understandings have rarely permeated governmental or academic discourse beyond anecdotal contentions. Thus, the present argument provides an empirical assessment of the complex, non-state policing landscape beyond the formal state apparatus; examines definitions and structures of such community-based policing activities; and explores issues related to co-opting this non-state security ‘otherness’ into more formal relations with the state.

Controlling the Shadow Trade

From tackling illicit flows of small arms to combating nuclear smuggling, the shadow trade has become a central target of attempts to control the means of violence. This article argues that much of this practice and literature is framed in unhelpful terms that posit two distinct worlds, an upperworld and underworld, that separates illicit flow networks from the familiar world of state security policy. This implies that the possibilities for controlling the shadow trade are limited or require expansive and expensive controls. The article then examines the formation of illicit flow networks, drawing on examples including narcotics, small arms, nuclear materials, nuclear technology, major conventional arms, dual use technologies, and chemical weapons precursors; and finds that state and hybrid actors rather than extensive private networks are constitutive of illicit networks in many ways. It concludes by reclaiming hope for controlling the means of violence in this hybridity.

Citizens as Social Work Educators in a Post-Conflict Society: Reflections from Northern Ireland

ABSTRACT This paper examines how service users and carers can contribute to social work education in a post conlict society. A small-scale study undertaken in Northern Ireland is used as a case study to show how such citizens can potentially critically contribute to social work students’ understanding of the impact of conlict on individuals, groups and communities. The need to appreciate the effects of such community division is now a core knowledge requirement of the social work curriculum in Northern Ireland. The article reports on research indings with service users, carers and agency representatives which points to ways in which social work students can achieve a critical understanding of the impact of conlict. Northern Ireland, in this way, is presented as a divided society, still in a state of adjustment and evolution, following a period of protracted community strife and violence. The author suggests that individuals who have been directly affected by conlict can contribute in an informed and critical way to social work students’ developing knowledge and experience in an important area of their professional competence and understanding of anti-oppressive practice more broadly.

Can Civil Society Succeed Where Elites Have Failed in the War on Sectarianism? Towards an infinitely demanding politics for the North

Caught between the well-armed imaginations of paramilitary organisations competing for the hearts and minds of a divided population, and state engineering of a liberal peace, civil society's impact on Northern Ireland's identity politics was limited during the thirty-year conflict. Specifically, the community and voluntary sector itself has tended to replicate as much as it challenged patterns of segregation in many of its own structures. With plans set out in the Northern Ireland Executive's Programme for Government (2008-11) to engage civil society in opening a new era of ‘good relations’ work to counter sectarianism and racism, civil society organisations will face a complex terrain, facing scepticism about their contribution to peace-making before the Good Friday Agreement, and working in a post-Agreement environment marked by continuing elite and communal antagonism demonstrated by the crisis at the turn of 2009 over devolution of justice and policing powers to the Northern Ireland Executive. A significant aspect of the resolution was a belated agreement by Sinn Fein and the DUP on a new community relation strategy, Cohesion, Sharing and Integration. This article suggests that civil society has a significant role to play in encouraging communities to confront the contradictions and tensions that continue to haunt the political architects of the Good Friday Agreement by affirming a radical and contingent vision of democracy as democratisation at a distance from the identity-saturated politics of the state-region of Northern Ireland. It draws on the work of Simon Critchley, Emmanuel Levinas and Wendy Brown, to offer an approach to identity politics in post-conflict Northern Ireland, focusing on the future orientation of civil society.

Influence of molten-state annealing on the phase structure and crystallization behaviour of high impact polypropylene copolymer

The phase structure evolution of high impact polypropylene copolymer (IPC) during molten-state annealing and its influence on crystallization behaviour were studied. An entirely different architecture of the IPC melt was observed after being annealed, and this architecture resulted in variations of the crystallization behaviour. In addition, it was found that the core-shell structure of the dispersed phase was completely destroyed and the sizes of the dispersed domains increased sharply after being annealed at 200 degrees C for 200 min. Through examination of the coarseness of the phase morphology using phase contrast microscopy (PCM), it was found that a co-continuous structure and an abnormal 'sea-island' structure generally appeared with an increase in annealing time. The original matrix PP component appeared as a dispersed phase, whereas the copolymer components formed a continuous 'sea-island' structure. This change is ascribed to the large tension induced by solidification at the phase interface and the great content difference between the components. When the temperature was reduced the structure reverted to its original form. With increasing annealing time, the spherulite profiles became more defined and the spherulite birefringence changed from vague to clear. Overall crystallization rates and nucleation densities decreased, but the spherulite radial growth rates remained almost constant, indicating that molten-state annealing mainly affects the nucleation ability of IPC, due to a coarsened microstructure and decreased interface area. (C) 2011 Elsevier Ltd. All rights reserved.