Electron impact excitation of Mo XXXIV

Energy levels and radiative rates for transitions among the lowest 60 fine-structure levels belonging to the (1s(2)) 2s(2)2p(5), 2s2p(6), and 2s(2)2p(4)3l configurations of F-like Mo XXXIV have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have also been computed over a wide energy range below 3200 Ry. using the Dirac Atomic R-matrix Code. Resonances have been resolved in a fine energy mesh in order to calculate the effective collision strengths. Results for radiative rates, collision strengths, and excitation rates are presented for transitions from the lowest three levels to higher lying states. Comparisons with other available results are made, and the accuracy of the present data is assessed. Energy levels are expected to be accurate to within 1%, while other parameters are probably accurate to better than 20%.

Numerical ‘health check’ for scientific codes: the CADNA approach

Scientific computation has unavoidable approximations built into its very fabric. One important source of error that is difficult to detect and control is round-off error propagation which originates from the use of finite precision arithmetic. We propose that there is a need to perform regular numerical `health checks' on scientific codes in order to detect the cancerous effect of round-off error propagation. This is particularly important in scientific codes that are built on legacy software. We advocate the use of the CADNA library as a suitable numerical screening tool. We present a case study to illustrate the practical use of CADNA in scientific codes that are of interest to the Computer Physics Communications readership. In doing so we hope to stimulate a greater awareness of round-off error propagation and present a practical means by which it can be analyzed and managed.

Devolving Housing Policy and Practice in Northern Ireland 1998 - 2002

This paper reviews the effect of devolution on housing policy and practice in Northern Ireland. It outlines the history and context of devolution and housing policy in Northern Ireland, including the legacy and persistence of intense social conflict. Current devolution arrangements are reviewed, including the implications of enforced coalition for policy governance. The paper focuses on three dimensions of housing and housing-related policy development and implementation: social housing, especially the distinctive history and changing organisation of social housing provision; policies affecting the housing market, including the changing regime for spatial planning; and, regeneration and tenant participation. The paper argues that housing policy has tended to converge with policies in England, rather than moving towards a distinctively local agenda. Local political agendas remain dominated by disagreements over constitutional status, thus policy formulation is determined more by officials than by elected politicians.