The paradox of the Casimir force in inhomogeneous transformation media

It has recently been argued that Casimir-Lifshitz forces depend in detail on the microphysics of a system; calculations of the Casimir force in inhomogeneous media yield results that are cutoff-dependent. This result has been shown to hold generally. But suppose we introduce an inhomogeneous metamaterial into a cavity that effectively implements a simple distortion of the coordinate system. Considered in its 'virtual space', the optical properties of such a material are homogeneous and consequently free from the cutoff-dependency associated with inhomogeneous media. This conclusion should be reconciled with recent advances in our understanding of Casimir-Lifshitz forces. We consider an example of such a system here and demonstrate that, whilst the size of the Casimir force is modified by the inhomogeneous medium, the force is cutoff-independent and can be stated exactly. The apparent paradox dissolves when we recognise that an idealised metamaterial that could implement a virtual geometry for all frequencies would be devoid of internal scattering, and would not give rise to a cutoff-dependency in the Casimir force for that reason.Comment: 7 page

Colored filters improve exclusion of perceptual noise in visually symptomatic dyslexics

Dyslexic individuals have deficits in detecting visual stimuli embedded in high levels of perceptual noise. Here we show that visually symptomatic dyslexics, who otherwise had elevated contrast thresholds for discriminating symbols in visual noise, had thresholds similar to non-dyslexics when wearing colored filters. These findings provide evidence that colored filters, which minimize the visual distortions and discomfort of dyslexics when reading, improve dyslexics' noise exclusion to normal levels

Not the Last Word

English and American Literature and Languag

Subjects of Triumph and Literary History: Dido and Petrarch in Petrarch's Africa and Trionfi

English and American Literature and Languag

Goitre in a South Wales valley

Goitre is a disease which is prevalent in many countries in all parts of the world. Its existence has been recognised for thousands of years, and it remains one of the commonest conditions to be seen in medical practice at the present time.As a newcomer to Aberdare, the writer rias immediately impressed by the fact that thyroid swellings were extremely common. They were to be seen everywhere, and they excited no comment. Further investigation showed that a definite proportion of the population suffered from this malady.The town is one of the mining towns of South Wales. There are no other industries of any importance. The subjects of the investigation are patients in a large general practice. It will be the endeavour of this article to try to explain why goitre should be so common in this locality, and this neighbourhood alone will be considered.As the investigation was carried out in general practice, the findings are the result of clinical examination entirely, histological examination being out of the question except in the few cases where operative assistance was necessary