The amplitude and phase of the pressure in the field of a rectangular piston, assumed vibrating within an infinite, rigid baffle, are examined theoretically for ranges down to the order of the piston length. Various laws of behavior of this field, both on and away from the acoustic axis, are deduced. An indication is given of the errors introduced by the approximations used. Such experimental evidence as is available supports the theory. Simple means are provided for constructing curves of axial pressure amplitude and phase for any ratio of length to breadth of the radiating surface, and a method is suggested for predicting the long-range axial pressure of a rectangular piston from measurements taken well within the latter's Fresnel region. The near fields of a rectangular and a circular piston are compared. That of the rectangular piston produces the more useful approximation to a plane wave.

Rare diseases are complex and difficult to diagnose, with parents and caregivers often reporting significant delays in receiving a definitive diagnosis. Following diagnosis, parents and caregivers often feel overwhelmed with emotions, including relief, guilt, and shock. The culmination of this emotional burden may lead to a deterioration of psychological health, ultimately reaching a stage where the parents struggle to cope. A systematic literature review was conducted of the articles on this topic by searching the electronic database, PubMed. Further studies were retrieved from a reference listing of relevant articles and consultation with experts in the field. The review was based on the guidance in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. The initial search identified 1276 articles, of which 37 met the inclusion criteria and were included in this review. The literature revealed key factors that appeared to contribute to psychological stress, including prolonged diagnostic odyssey, poor diagnostic delivery, lack of information and specialist knowledge, and convoluted healthcare systems. This review reinforces the need for psychological support amongst parents and caregivers of children with a rare disease at the time of diagnosis. The results of this literature review will be used to develop a statement of good practice for the support of parents and caregivers when a rare disease diagnosis is given.

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