Effects in polarimetry of interference within wave plates

Multiple-beam interference within wave plates is investigated in terms of the detrimental effects it produces in the data of stellar spectropolarimetry. It is noted that spectral fringe structures occur in the phase delay, the polarizance and, for Pancharatnam designs, the reference axis of the wave plate. The natures of the problems are exposed by considering typical wave plates and experimental procedures used in linear and circular spectropolarimetry. It is demonstrated that the chief bane of accurate measurements is the presence of polarizance fringes, but which can be alleviated by the choice of experimental procedure. For spectral circular polarization studies, problems of cross-talk from any linear polarization present in the source are especially severe. In principle the effects of fringing can be removed in data reductions by calibration measurements of a set of linear polarization standard stars displaying different vibration azimuths and, for circular polarization measurements, knowledge of the linear polarization characteristics of the investigated star must also be known

Adult education between the wars - the curious case of the Selborne Lecture Bureau

‘Independent’ lecture agencies are an important but neglected element in the history of education. Between 1918 and 1939, the Selborne Lecture Bureau was a significant national provider of adult education in Britain, both in its own right and as a supplier of lecture(r)s to Women’s Institutes and other bodies, and it pioneered the use of films in schools. For a brief period, it was an ‘educational’ vehicle for the Empire Marketing Board with a programme of over 2,400 lectures in 1929. The Bureau originated in the early 20th century split between the conservative (and male) traditions of natural history and the radical (and female) campaigning (anti) plumage movement that produced the RSPB. The inter-War history of the Selborne Lecture Bureau provides a counterpoint to conventional accounts of adult education between the two World Wars, representing an influential ‘third stream’ alongside the ‘liberal tradition’ and growing state and local authority provision

Ambiguity reduction by objective model selection, with an application to the costs of the EU 2030 climate targets

I estimate the cost of meeting the EU 2030 targets for greenhouse gas emission reduction, using statistical emulators of ten alternative models. Assuming a first-best policy implementation, I find that total and marginal costs are modest. The statistical emulators allow me to compute the risk premiums, which are small, because the EU is rich and the policy impact is small. The ensemble of ten models allows me to compute the ambiguity premium, which is small for the same reason. I construct a counterfactual estimate of recent emissions without the climate policy and use that to test the predictive skill of the ten models. The models that show the lowest cost of emission reduction also have the lowest skill for Europe in recent times

Performance prediction tools for low impact building design

IT systems are emerging that may be used to support decisions relating to the design of a built enviroment that has low impact in terms of energy use and environmental emissions. This paper summarises this prospect in relation to four complementary application areas: digital cities, rational planning, virtual design and Internet energy services

The differing approach to commercial litigation in the European Court of Justice and the courts of England and Wales I

Article by Sir Anthony Clarke published in Amicus Curiae - Journal of the Society for Advanced Legal Studies. The Journal is produced by the Society for Advanced Legal Studies at the Institute of Advanced Legal Studies, University of London

Period determinations of spotted stars

The general behaviours of photometric, radial velocity and polarimetric observational investigations are explored in terms of the signals generated by a spot or patch in co-rotation with a star. It is demonstrated that the results of any period analysis of data depends on the nature of the chosen measurement diagnostic. Unlike photometry, analysis of radial velocity measurements is likely to provide considerable power at periods corresponding to the harmonics of the stellar rotational period. This conclusion may have bearing on Harmanec's "submultiple period scenario" in connection with the understanding of the behaviour of early-type stars. Period analysis of polarimetric data is also likely to provide strong power in the harmonics of the fundamental rotational period. This analysis of the signals from the three basic observational diagnostics shows the dangers of simply using one measurement parameter alone to investigate stellar temporal behaviour and how interpretational confusion can arise when the results from different exercises are compared