Optimising the use of virtual and conventional simulation: a clinical and economic analysis

Background and purpose: Currently, optimal use of virtual simulation for all treatment sites is not entirely clear. This study presents data to identify specific patient groups for whom conventional simulation may be completely eliminated and replaced by virtual simulation. Sampling and method: Two hundred and sixty patients were recruited from four treatment sites (head and neck, breast, pelvis, and thorax). Patients were randomly assigned to be treated using the usual treatment process involving conventional simulation, or a treatment process differing only in the replacement of conventional plan verification with virtual verification. Data were collected on set-up accuracy at verification, and the number of unsatisfactory verifications requiring a return to the conventional simulator. A micro-economic costing analysis was also undertaken, whereby data for each treatment process episode were also collected: number and grade of staff present, and the time for each treatment episode. Results: The study shows no statistically significant difference in the number of returns to the conventional simulator for each site and study arm. Image registration data show similar quality of verification for each study arm. The micro-costing data show no statistical difference between the virtual and conventional simulation processes. Conclusions: At our institution, virtual simulation including virtual verification for the sites investigated presents no disadvantage compared to conventional simulation.

Extension of the Ye and Shreeve group contribution method for density estimation of ionic liquids in a wide range of temperatures and pressures

An extension of the Ye and Shreeve group contribution method [C. Ye, J.M. Shreeve, J. Phys. Chem. A 111 (2007) 1456–1461] for the estimation of densities of ionic liquids (ILs) is here proposed. The new version here presented allows the estimation of densities of ionic liquids in wide ranges of temperature and pressure using the previously proposed parameter table. Coefficients of new density correlation proposed were estimated using experimental densities of nine imidazolium-based ionic liquids. The new density correlation was tested against experimental densities available in literature for ionic liquids based on imidazolium, pyridinium, pyrrolidinium and phosphonium cations. Predicted densities are in good agreement with experimental literature data in a wide range of temperatures (273.15–393.15 K) and pressures (0.10–100 MPa). For imidazolium-based ILs, the mean percent deviation (MPD) is 0.45% and 1.49% for phosphonium-based ILs. A low MPD ranging from 0.41% to 1.57% was also observed for pyridinium and pyrrolidinium-based ILs.

Peer-mentoring for first-time mothers from areas of socio-economic disadvantage: a qualitative study within a randomised controlled trial

Objective: To explore the difficulties experienced by lay-workers, women and health professionals involved in a peer-mentoring programme for first-time mothers living in socially disadvantaged areas. Design: Qualitative study; semi-structured interviews with lay-worker peer-mentoring programme participants at two separate stages of the programme (antenatal and postnatal). Setting: Community based. Participants: 11 women receiving peer-mentoring support (from first hospital antenatal visit to one year postnatal); 11 lay-workers; 2 research midwives. Results: Lay-workers had difficulty initiating contact with women and failure to establish contact affected their morale adversely. They felt that women understood their intended role poorly and attempted to develop relationships with them by sharing personal experiences and offering friendship; women who participated in the programme appreciated this. Developing a peer-mentor relationship was difficult if women lacked interest in the programme or in continuing contact. External influences on peer-mentoring uptake and delivery included family and friends who could prevent or encourage women’s participation and cause difficulties for the lay-worker both in delivering support and arranging follow-up. Lay-workers providing support to women from a different ethnic background experienced difficulties relating to both language and culture: these were perceived to affect peer-mentor relationships adversely. Major personal difficulties for lay-workers related to time constraints in reconciling mentoring requirements with demands of family and other work. Informing midwives of these difficulties helped identify solutions through training and ongoing professional support for the lay-workers. Conclusions: Lay-worker peer support is appreciated by first time mothers but difficulties in initiating contact, developing peer-mentor relationships and external influences such as family, ethnicity and time constraints are relevant to poor uptake and high staff turnover. In developing peer support programmes, awareness of potential difficulties and of how professional support can help resolve these should improve uptake and thus optimise the evaluations of their effectiveness.

Economic cost of age-related macular degeneration: a review of recent research

As the population of most developed countries ages so the prevalence of diseases such as age-related macular degeneration (AMD) are likely to increase. To facilitate planning and informed debate regarding making provisions for this disease it is important that we have a clear understanding of the economic impact of visual impairment associated with AMD. In this paper we assess the state of current knowledge based on a review of published evidence in scientific journals. Based on our assessment of the evidence we argue that the paucity of research studies on the subject and wide variation in estimates produced from the few studies available make it difficult to assess with confidence the likely average direct cost-of-illness associated with AMD. We further argue that significant gaps in our understanding of the costs of AMD (particularly in respect of indirect costs) also exist. Current research should be augmented by more comprehensive studies.

Measurement of Quenching Coefficients and Developement of Calibration Methods for Quantitative Spectroscopy of Plasma at Elevated Pressures

Measurements of collisional de-excitation (quenching) coefficients required for the interpretation of emission and fluorescence spectroscopic measurements are reported. Particular attention is turned on argon transitions which are of interest for actinometric determinations of atomic ground state populations and on fluorescence lines originating from excited atoms and noble gases in connection with two-photon excitation (TALIF) of atomic radicals. A novel method is described which allows to infer quenching coefficients for collisions with molecular hydrogen of noble gas states in the energy range up to 24 eV. The excitation is performed in these experiments by collisions of energetic electrons in the sheath of an RF excited hydrogen plasma during the field reversal phase which lasts about 10 ns. We describe in addition a calibration method - including quenching effects - for the determination by TALIF of absolute atomic radical densities of hydrogen, nitrogen and oxygen using two-photon resonances in noble gases close by the resonances of the species mentioned. The paper closes with first ideas on a novel technique to bypass quenching effects in TALIF by introducing an additional, controllable loss by photoionization that will allow quenching-free determination of absolute atomic densities with prevalent nanosecond laser systems in situations where collisional de-excitation dominates over spontaneous emission.